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Journal of Separation Science



Wiley Online Library : Journal of Separation Science



Published: 2018-02-01T00:00:00-05:00

 



Analysis of new psychoactive substances in human urine by ultra high performance supercritical fluid and liquid chromatography: Validation and comparison

2018-02-20T07:50:34.443965-05:00

New psychoactive substances represent serious social and health problem as tens of new compounds are detected in Europe annually. They often show structural proximity or even isomerism which complicates their analysis. Two methods based on ultra high performance supercritical fluid chromatography and ultra high performance liquid chromatography with mass spectrometric detection were validated and compared. A simple dilute-filter-and-shoot protocol utilizing propan-2-ol or methanol for supercritical fluid or liquid chromatography, respectively, was proposed to detect and quantify 15 cathinones and phenethylamines in human urine. Both methods offered fast separation (<3 min) and short total analysis time. Precision was well below 15% with a few exceptions in liquid chromatography. Limits of detection in urine ranged from 0.01 to 2.3 ng/mL, except for cathinone (5 ng/mL) in supercritical fluid chromatography. Nevertheless, this technique distinguished all analytes including four pairs of isomers, while liquid chromatography was unable to resolve fluoromethcathinone regioisomers. Concerning matrix effects and recoveries, supercritical fluid chromatography produced more uniform results for different compounds and at different concentration levels. This work demonstrates the performance and reliability of supercritical fluid chromatography and corroborates its applicability as an alternative tool for analysis of new psychoactive substances in biological matrixes. This article is protected by copyright. All rights reserved



Amino acid racemization and its relation to geochronology and archaeometry

2018-02-20T04:50:34.262126-05:00

Amino acid racemization, used as a method of relative and quantitative dating of fossils, evaluates the degree of postmortem conversion of l to d amino acid enantiomers. While extensively utilized, this method has garnered confusion due to controversial age estimates for human fossils in North America in the 1970s. This paper explains the age controversy and aftermath, current chromatographic methods used in research, mathematical calibration models, and a short synopsis of other dating techniques in geochronology and archaeometry. This article is protected by copyright. All rights reserved



Simple method for the determination of personal care product ingredients in lettuce by ultrasound-assisted extraction combined with solid-phase microextraction followed by GC–MS

2018-02-19T11:20:34.39778-05:00

A simple method for the simultaneous determination of personal care product ingredients: galaxolide, tonalide, oxybenzone, 4-methylbenzyliden camphor, padimate-o, 2-ethylhexyl methoxycinnamate, octocrylene, triclosan and methyl triclosan in lettuce by ultrasound-assisted extraction combined with solid-phase microextraction followed by gas chromatography with mass spectrometry was developed. Lettuce was directly extracted by ultrasound-assisted extraction with methanol, this extract was combined with water, extracted by solid-phase microextraction in immersion mode and analyzed by gas chromatography with mass spectrometry. Good linear relationships (25–250 ng g−1, R2 > 0.9702) and low detection limits (1.0–25 ng g−1) were obtained for analytes along with acceptable precision for almost all analytes (RSDs < 20%). The validated method was applied for the determination of personal care product ingredients in commercial lettuce and lettuces grown in soil and irrigated with the analytes, identifying the target analytes in leaves and roots of the latter. This procedure is a miniaturized and environmentally friendly proposal which can be a useful tool for quality analysis in lettuce. This article is protected by copyright. All rights reserved



Effect of the flow profile on separation efficiency in pressure-assisted reversed-polarity capillary zone electrophoresis of anions: Simulation and experimental evaluation

2018-02-19T10:20:24.210736-05:00

Capillary electrophoresis connected to electrospray ionization mass spectrometry is a promising combination to analyze complex biological samples. The use of sheathless electrospray ionization interfaces, such as a porous nanoelectrospray capillary emitter, requires the application of forward flow (either by pressure or electroosmosis) to maintain the electrospray process. The analysis of solute molecules with strong negative charges (e.g., aminopyrenetrisulfonate labeled glycans) necessitates a reversed-polarity capillary electrophoresis separation mode, in which case the electroosmotic flow is counter current, thus pressure assistance is necessary. In this study, we compared the effect of forced convection with and without counter electroosmotic flow on the resulting separation efficiency in capillary electrophoresis based on flow profile simulations by computational fluid dynamics technique and by actual experiments. The efficiencies of the detected peaks were calculated from the resulting electropherograms and found approximately 790 000 plates/m for electrophoresis with counter electroosmotic flow, 16 000 plates/m with pressure only (such as would be in open tubular liquid chromatography) and 400 000 plates/m for electrophoresis with simultaneous counter electroosmotic flow and forward pressure assistance, which validates the simulation data. This article is protected by copyright. All rights reserved



Application of off-line two-dimensional high-performance countercurrent chromatography on the chloroform-soluble extract of Cuscuta auralis seeds

2018-02-16T00:50:34.791464-05:00

In this study, the chloroform-soluble extract of C. auralis was separated successfully using off-line two-dimensional high-performance countercurrent chromatography, yielding a γ-pyrone, two alkaloids, a flavonoid and four lignans. The first-dimensional countercurrent separation using a methylene chloride/methanol/water (11:6:5, v/v/v) system yielded three sub-fractions (fractions I–III). The second-dimensional countercurrent separations, conducted on fractions I–III using n-hexane/ethyl and acetate/methanol/acetic acid (5:5:5:5:0, 3:7:3:7:0 and 1:9:1:9:0.01, v/v/v/v/v) systems, gave maltol (1), (−)-(13S)-cuscutamine (2), (+)-(13R)-cuscutamine (3), (+)-pinoresinol (4), (+)-epipinoresinol (5), kaempferol (6), piperitol (7) and (9R)-hydroxy-d-sesamin (8). To the best of our knowledge, maltol was identified for the first time in Cuscuta species. Furthermore, this report details the first full assignment of spectroscopic data of two cuscutamine epimers, (−)-(13S)-cuscutamine and (+)-(13R)-cuscutamine. This article is protected by copyright. All rights reserved



Application of nano-perlite as a new natural sorbent in preconcentration of three organophosphorus pesticides by microextraction in packed syringe coupled with GC–MS

2018-02-15T04:50:25.007887-05:00

A rapid, low-cost, and simple method is proposed based on a miniaturized solid-phase extraction named microextraction in packed syringe coupled with gas chromatography and mass spectrometry for the preconcentration and determination of some organophosphorous pesticides including diazinon, ethion, and malathion. For the first time, natural nano-perlite is used as a safe sorbent. Based on this technique, the analytes are adsorbed on the solid phase and then eluted by a desorbing solvent. The influence of some important parameters such as the solution pH, and type and volume of the organic desorption solvent on the microextraction efficiency of the selected pesticide technique is investigated. The proposed method showed a good linearity in the range of 1.0–35.0 μg L‒1 for ethion and 0.4–30.0 μg L‒1 for both diazinon and malathion. The limits of detection in the range of 0.1–0.38 μg L‒1 were obtained using the selected ion-monitoring mode of the mass spectrometer. The reproducibility of the method was found to be in the range of 2.8–8.9% for the studied pesticides. To evaluate the matrix effect, the developed method is also applied to the preconcentration and determination of the selected pesticides in real water samples. This article is protected by copyright. All rights reserved



Evaluation and validation of an ion mobility quadrupole time-of-flight mass spectrometry pesticide screening approach

2018-02-15T03:20:23.740526-05:00

An ion mobility quadrupole time-of-flight mass spectrometry-based pesticide suspect screening methodology was developed and validated covering 20 plant-derived food matrices deriving from six commodity groups of different complexity according to the actual European Commission document SANTE/11813/2017 applying a QuEChERS sample preparation protocol. The method combines ultra-performance liquid chromatography travelling-wave ion mobility and quadrupole time-of-flight mass spectrometry. Besides the determination of the physicochemical property collision cross section and the establishment of a corresponding scientific suspect screening database comprising 280 pesticides, for several pesticides different protomers, sodium adducts, as well as dimers were identified in ion mobility spectrometry traces. Additionally, collision cross section values were included in the validation requirements regarding chromatography and mass spectrometry for the detection of pesticides. A collision cross section value window was analyzed within a tolerable error of ± 2%. For this cross-matrix validation screening detection limits were determined at concentration levels of 0.100 mg/kg (84% of the original pesticide scope), at 0.010 mg/kg (56%), and at 0.001 mg/kg (21%). By application of ion mobility spectrometry, the compound identification was improved due to independence of commodity of concern and concentration levels of analyte molecules, as false assignments are reduced by application of a collision cross section range. This article is protected by copyright. All rights reserved



Elution–extrusion counter-current chromatography separation of six pairs of isomeric iridoids from Cornus officinalis Sieb. et Zucc. guided by ion current extraction in mass spectrometry

2018-02-14T05:20:49.073122-05:00

A mass spectrometry guided elution–extrusion counter-current chromatography protocol was developed to separate chemical components from Cornus officinalis Sieb. et Zucc. Ion current extraction, a mass spectrometry based data post-acquisition method, was utilized to boost the separation power and scope of counter-current chromatography technique in this study. As a peak re-picking and denoising tool, ion current extraction was carried out to process the liquid chromatography with mass spectrometry and the counter-current chromatography with mass spectrometry data. So the target components were re-acquired in the created extracted ion current patterns with enhanced responses and diminished background noise, which facilitated the distribution constant determination (by liquid chromatography with extracted ion current) and the targets fractionation (by counter-current chromatography with extracted ion current). Under the guidance of the extracted ion currents of the target components and with the support of elution–extrusion mode in the counter-current chromatography separation, six pairs of minor iridoid isomers were obtained in shortened experimental duration. Besides, a reciprocal shifted symmetry plot was established to represent the elution–extrusion counter-current chromatography chromatogram. The results demonstrated the capability of the ion current extraction guided elution–extrusion counter-current chromatography protocol in discovery, analysis, and fractionation of low-concentration and structurally similar chemicals from a complicated sample. This article is protected by copyright. All rights reserved



Evaluation of solid-phase extraction procedures for the quantitation of venlafaxine in human saliva by HPLC

2018-02-13T06:20:30.381663-05:00

In recent years, the use of human saliva for diagnostic purposes has evoked great interest. Thus, the aim of this study was to choose the optimal solid-phase extraction cartridges and extraction solvents for the quantitation of venlafaxine in saliva. Blank saliva samples spiked with venlafaxine concentrations between 25 and 750 ng/mL were analyzed using five solid-phase extraction columns (C18, C8, Strata-X, Strata-X-C, and Strata-X-AW), washing solvents (deionized water, phosphate buffer at pH 5.5, and their mixtures with methanol) and elution solvents (methanol, acetonitrile, and their mixtures with 25% ammonia). A high-performance liquid chromatography system was used to quantify venlafaxine in saliva. The results of this study revealed that 9 out of 25 procedures enabled quantitation of venlafaxine in the tested concentration range. The procedure that used a C18 cartridge, a mixture of methanol and deionized water as the washing solvent and methanol as the elution solvent was the most effective and allowed quantitation of all venlafaxine concentrations with an acceptable recovery. In contrast, the Strata-X-C cartridge could not detect venlafaxine at the lowest concentration (25 ng/mL). The data acquired from the HPLC system were confirmed by a multivariate data analysis. This article is protected by copyright. All rights reserved



A novel sorbent based on carbon nanotube/amino-functionalized sol–gel for the headspace solid-phase microextraction of α-bisabolol from medicinal plant samples using experimental design

2018-02-13T02:51:31.846631-05:00

A novel sol–gel coating on a stainless-steel fiber was developed for the first time for the headspace solid-phase microextraction and determination of α-bisabolol with gas chromatography and flame ionization detection. The parameters influencing the efficiency of solid-phase microextraction process, such as extraction time and temperature, pH and ionic strength were optimized by experimental design method. Under optimized conditions, the linear range was between 0.0027 and 100 μg/mL. The relative standard deviations determined at 0.01 and 1.0 μg/mL concentration levels (n = 3) respectively were as follows: intraday relative standard deviations 3.4 and 3.3%; interday relative standard deviations 5.0 and 4.3%; fiber-to-fiber relative standard deviations 6.0 and 3.5%. The relative recovery values were 90.3 and 101.4% at 0.01 and 1.0 μg/mL spiking levels, respectively. The proposed method was successfully applied to various real samples containing α-bisabolol. This article is protected by copyright. All rights reserved



Simultaneous determination and pharmacokinetics study of four quinones in rat plasma by UHPLC–ESI-MS/MS after the oral administration of Qianzhi capsules

2018-02-13T02:50:43.461763-05:00

A sensitive, specific, and accurate ultra high performance liquid chromatography with electrospray ionization tandem mass spectrometry method was developed and validated for the simultaneous quantification of purpurin, munjistin, mollugin and alizarin from Qianzhi capsules in rat plasma. Chromatographic separation was performed on an Aglient Eclipse Plus C18 RRHD column with a mobile phase consisting of methanol and 5 mM ammonium acetate/water with gradient elution. The analytes were quantified on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring mode and switching the electrospray ion source polarity with positive electrospray ionization in a single run. Samples were pretreated by liquid–liquid extraction with cyclohexane. The intra- and inter-day precision and accuracy of the assay were within acceptable ranges. Matrix effects for all of the analytes were between 90.16 and 100.21%. The average recovery ranged from 75.38 to 88.96%. This method was successfully applied to study the pharmacokinetic parameters of the four compounds in rat plasma after oral administration of Qianzhi capsules.Four quinones could be rapidly absorbed into blood (tmax, 0.80∼1.93 h) and eliminated relatively slowly (t1/2, 8.07∼11.97 h). The results might be helpful for guiding the clinical application of Qianzhi capsules in the future. This article is protected by copyright. All rights reserved



Graphene-doped electrochemical copolymer coating of 2,2-bithiophene and 3-methylthiophene for the highly effective solid-phase microextraction of volatile benzene homologues

2018-02-13T02:21:49.509851-05:00

We report the electrochemical fabrication of a poly(2,2-bithiophene-co-3-methylthiophene)-graphene composite coating and its application in the headspace solid-phase microextraction and gas chromatography determination of benzenes (i.e., bromobenzene, 4-bromotoluene, 2-nitrotoluene, 3-nitrotoluene, 1,2,4-trichlorobenzene). The coating was uniform and showed cauliflower-like microstructure. It had high thermal stability (up to 375°C) and could be used for at least 180 times of solid-phase microextraction without a decrease of extraction performance. Furthermore, it presented high extraction capacity for the benzenes due to the hydrophobic effect and π–π interaction between the analytes and the coating. Under optimized extraction conditions, good linearity (correlation coefficients higher than 0.9946), wide linear range (0.01–50 μg L−1), low limits of detection (5.25–12.5 ng L−1) were achieved for these analytes. The relative standard deviation was lower than 5.7% for five successive measurements with one fiber, and the relative standard deviation for fiber-to-fiber was 4.9–6.8% (n = 5). The solid-phase microextraction and gas chromatography method was successfully applied for the determination of three real samples, and the recoveries for standards added were 89.6–106% for nail polish, 85.8–110% for hair dye and 90–106.2% for correction fluid, respectively. This article is protected by copyright. All rights reserved



Simultaneous determination of 29 pharmaceuticals in fish muscle and plasma by ultrasonic extraction followed by SPE–UHPLC–MS/MS

2018-02-12T10:50:26.698169-05:00

A confirmatory method for the simultaneous detection of 29 pharmaceuticals in fish muscle and plasma was developed by using solid-phase extraction combined with ultra high performance liquid chromatography and tandem mass spectrometry. Fish samples were extracted with methanol and enriched using Oasis HLB solid-phase extraction columns in one step. Twenty-nine target pharmaceuticals were quantified by the internal standard method and the calibration curves showed good linearity in a wide range with determination coefficients of greater than 0.913. The detection limits of the pharmaceuticals ranged from 0.01 to 2.00 μg/kg (μg/L). The applicability of the method was checked by precision and recovery experiments. The average recoveries of the 29 pharmaceuticals were between 61 and 111%, and all the relative standard deviations were below 25%. Our reported method has been demonstrated to be sensitive, convenient, rapid and reliable for the simultaneous determination of 29 pharmaceuticals in fish muscle and plasma. Real sample determination showed that 25 and 9 of the 29 compounds were detected in fish muscle and plasma, respectively. This article is protected by copyright. All rights reserved



β-Cyclodextrin-modified three-dimensional graphene oxide wrapped melamine foam for the solid-phase extraction of flavonoids

2018-02-12T04:20:27.888568-05:00

A new three-dimensional graphene oxide wrapped melamine foam was prepared and used as a solid-phase extraction substrate. β-Cyclodextrin was fabricated onto the surface of three-dimensional graphene oxide-wrapped melamine foam by a chemical covalent interaction. In view of a specific surface area and a large delocalized π electron system of graphene oxide, combing with a hydrophobic interior cavity and a hydrophilic peripheral face of β-cyclodextrin, the prepared extraction material was proposed for the determination of flavonoids. In order to demonstrate the extraction properties of the as-prepared material, the adsorption energies were theoretically calculated based on periodic density functional theory. Static-state and dynamic-state binding experiments were also investigated, which revealed the monolayer coverage of flavonoids onto the β-cyclodextrin/graphene oxide wrapped melamine foams through the chemical adsorption. 1H NMR spectroscopy indicated the formation of flavonoids–β-cyclodextrin inclusion complexes. Under the optimum conditions, the proposed method exhibited acceptable linear ranges (2–200 μg L−1 for rutin and quercetin-3-O-rhamnoside; 5–200 μg L−1 for quercetin) with correlation coefficients ranging from 0.9979 to 0.9994. The batch-to-batch reproducibility (n = 5) was 3.5–6.8%. Finally, the as-established method was satisfactorily applied for the determination of flavonoids in Lycium barbarum (Goji) samples with relative recoveries in the range of 77.9–102.6 %. This article is protected by copyright. All rights reserved



Screening and analysis of potential active components in Shengxiong glucose injection using UHPLC coupled with photodiode array detection and MS/MS

2018-02-12T03:50:26.806168-05:00

Shengxiong glucose injection, a pharmaceutical preparation containing a water extract of the roots of Salvia miltiorrhizae and ligustrazine hydrochloride, is widely used in clinical to treat cardiovascular diseases in China. The chemical components of the water extract have been reported and the cardioprotective effects of the injection have been evaluated. However, the chemical constituents of the injection and their correlations with its pharmacological effects have not been established. In this study, thirteen chemical constituents of the injection have been identified or characterized by ultra high performance liquid chromatography with diode array detection and electrospray ionization quadrupole time-of-flight tandem mass spectrometry. Besides, the potential active compounds of this preparation that directly act on cardiac cells have been screened by cell extraction and ultra high performance liquid chromatography targeted multiple reaction monitoring. As a result, eight potentially active compounds, danshensu (1), ligustrazine hydrochloride (4), salvianolic acid I/H (7), lithospermic acid (8), salvianolic acid D (9), rosmarinic acid (10), salvianolic acid B (12), and salvianolic acid C (13), were obtained and structurally characterized from the 11 target compounds used for screening. The liquid chromatography with quadrupole time-of-flight mass spectrometry and liquid chromatography with multiple reaction monitoring tandem mass spectrometry combination method has demonstrated its potency for the screening, detection, and structural identification of bioactive compounds in a complex matrix. This article is protected by copyright. All rights reserved



Rapid and sensitive detection of the phenoxy acid herbicides in environmental water samples by magnetic solid-phase extraction combined with LC–MS/MS

2018-02-12T02:50:23.179596-05:00

Phenoxy acid herbicides are widely used herbicides that play an important role in improving the yield and quality of crops. However, some research has shown that this kind of herbicide is poisonous to human and animals. In this study, a rapid and sensitive method was developed for the detection of seven phenoxy acid herbicides in water samples based on magnetic solid phase extraction followed by liquid chromatography and tandem mass spectrometry. Magnetic amino-functionalized multi-walled carbon nanotubes were prepared by mixing bare magnetic Fe3O4 nanoparticles with commercial amino-functionalized multi-walled carbon nanotubes in water. Then the amino-functionalized multi-walled carbon nanotubes were used to enrich phenoxy acid herbicides from water samples based on hydrophobic and ionic interactions. The effects of experimental variables on the extraction efficiency have been studied in detail. Under the optimized conditions, the method validation was performed. Good linearities for seven phenoxy acid herbicides were obtained with squared regression coefficients ranging from 0.9971 to 0.9989. The limits of detection ranged from 0.01 to 0.02 μg/L. The method recoveries of seven phenoxy acid herbicides spiked at three concentration levels in a blank sample were from 92.3 to 103.2%, with inter- and intra-day relative standard deviations less than 12.6%. This article is protected by copyright. All rights reserved



Investigation of the chromatographic regulation properties of benzyl groups attached to bridging nitrogen atoms in a calixtriazine-bonded stationary phase

2018-02-10T04:50:51.846586-05:00

Two reversed-phase/anion-exchange mixed-mode stationary phases for high-performance liquid chromatography using calixtriazines as chromatographic ligands were investigated with Tanaka test solutes, monosubstituted benzenes, aromatic positional isomers, and inorganic anions. Calixtriazine as a chromatographic ligand has been reported previously, but the benzylated nitrogen-bridged calixtriazine bonded silica gel reported in this study is new. The experimental data showed that the calixtriazine platform is a unique chromatographic selector because its multiple active sites are available for different solutes and its chromatographic selectivity could be tuned by introducing substituent on the bridging nitrogen atoms present in the calixtriazine matrix. The synergistic effects of aromatic rings, nitrogen atoms, benzyl groups and tunable cavity in the host molecule influenced the separation selectivity by multiple retention mechanisms. Such hybrid stationary phases provide more versatility and have great potential in the analysis of complex samples. Moreover, the synthetic protocols presented herein may provide an alternative understanding on macrocyclic host–guest chemistry, leading to new and selective separation media. This article is protected by copyright. All rights reserved



Simple determination of some anti-dementia drugs in wastewater and human plasma samples by tandem dispersive liquid–liquid microextraction followed by HPLC

2018-02-10T04:25:56.542159-05:00

In this work, a simple method, namely, tandem dispersive liquid–liquid microextraction, with a high sample clean-up is applied for the rapid determination of the anti-dementia drugs rivastigmine and donepezil in wastewater and human plasma samples. This method, which is based upon two consecutive dispersive microextractions, is performed in 7 min. In the method, using a fast back-extraction step, the applicability of the dispersive microextraction methods in complicated matrixes is conveniently improved. This step can be performed in less than 2 min, and very simple tools are required for this purpose. To achieve the best extraction efficiency, optimization of the variables affecting the method was carried out. Under the optimized experimental conditions, the relative standard deviations for the method were in the range of 6.9–8.7%. The calibration curves were obtained in the range of 2–1100 ng mL−1 with good correlation coefficients, higher than 0.995, and the limits of detection ranged between 0.5 and 1.0 ng mL−1. This article is protected by copyright. All rights reserved



Simultaneous identification and quantification of bisphenol A and twelve bisphenol analogues in environmental samples using precolumn derivatization and UHPLC–MS/MS

2018-02-10T04:25:25.427795-05:00

A method for the identification and quantification of bisphenol A and 12 bisphenol analogues in river water and sediment samples combining liquid–liquid extraction, precolumn derivatization and ultra high performance liquid chromatography coupled with tandem mass spectrometry was developed and validated. Analytes were extracted from the river water sample using a liquid–liquid extraction method. Dansyl chloride was selected as a derivatization reagent. Derivatization reaction conditions affecting production of the dansyl derivatives were tested and optimized. All the derivatized target compounds were well separated and eluted in 10 min. Dansyl chloride labelled compounds were analysed using a high-resolution mass spectrometer with electrospray ionization in the positive mode, and the results were confirmed and quantified in the parallel reaction monitoring mode. The method validation results showed a satisfactory level of sensitivity. Linearity was assessed using matrix-matched standard calibration, and good correlation coefficients were obtained. The limits of quantification for the analytes ranged from 0.005 to 0.02 ng/mL in river water and from 0.15 to 0.80 ng/g in sediment. Good reproducibility of the method in terms of intra- and inter-day precision was achieved, yielding relative standard deviations of less than 10.1 and 11.6%, respectively. Finally, this method was successfully applied to the analysis of real samples. This article is protected by copyright. All rights reserved



Size-selective purification of hepatitis B virus-like particle in flow-through chromatography: Types of ion exchange adsorbent and grafted polymer architecture

2018-02-09T23:50:33.16818-05:00

Hepatitis B virus-like particles expressed in Escherichia coli were purified using anion exchange adsorbents grafted with polymer poly(oligo(ethylene glycol) methacrylate) in flow-through chromatography mode. The virus-like particles were selectively excluded, while the relatively smaller-sized host cell proteins were absorbed. The exclusion of virus-like particles was governed by the accessibility of binding sites (the size of adsorbents and the charge of grafted dextran chains) as well as the architecture (branch-chain length) of the grafted polymer. The branch-chain length of grafted polymer was altered by changing the type of monomers used. The larger adsorbent (90 μm) had an approximately twofold increase in the flow-through recovery, as compared to the smaller adsorbent (30 μm). Generally, polymer grafted adsorbents improved the exclusion of the virus-like particles. Overall, the middle branch-chain length polymer grafted on larger adsorbent showed optimal performance at 92% flow-through recovery with a purification factor of 1.53. A comparative study between the adsorbent with dextran grafts and the polymer grafted adsorbent shown that a better exclusion of virus-like particles was achieved with the absorbent grafted with inert polymer. The grafted polymer was also shown to reduce strong interaction between binding sites and virus-like particles, which preserved the particles’ structure. This article is protected by copyright. All rights reserved



Application of sunflower stalk-carbon nitride nanosheets as a green sorbent in the solid-phase extraction of polycyclic aromatic hydrocarbons followed by HPLC

2018-02-08T14:50:25.958458-05:00

A green biocomposite of sunflower stalks and graphitic carbon nitride nanosheets has been applied as a solid-phase extraction adsorbent for sample preparation of five polycyclic aromatic hydrocarbons in different solutions using high-performance liquid chromatography with UV detection. Before the modification, sunflower stalks exhibited relatively low adsorption to the polycyclic aromatic hydrocarbons extraction. The modified sunflower stalks showed increased adsorption to the analytes extraction due to the surface increasing and existence of a π–π interaction between the analytes and graphitic carbon nitride nanosheets on the surface. Under the optimal conditions, the limits of detection and quantification for five polycyclic aromatic hydrocarbons compounds could reach 0.4–32 and 1.2–95 ng L−1, respectively. The method accuracy was evaluated using recovery measurements in spiked real samples and good recoveries from 71 to 115% with relative standard deviations of less than 10% have been achieved. The developed method was successfully applied for polycyclic aromatic hydrocarbons determination in various samples: well water, tap water, soil, vegetable and barbequed meat (Kebab), with analytes contents ranging from 0.065 to 13.3 μg L−1. The prepared green composite as a new sorbent has some advantages including ease of preparation, low cost and good reusability. This article is protected by copyright. All rights reserved



Structure–property relationship study of the HPLC enantioselective retention of neuroprotective 7-[(1-alkylpiperidin-3-yl)methoxy]coumarin derivatives on an amylose-based chiral stationary phase

2018-02-08T08:50:33.450794-05:00

The enantiomer separation of a number of racemic 7-[(1-alkylpiperidin-3-yl)methoxy]coumarin derivatives, some of which show outstanding in vitro multitarget neuroprotective activities, was successfully achieved on a polysaccharide-based chiral stationary phase, bearing amylose tris(3,5-dimethylphenylcarbamate) as chiral selector, in normal polar mode (methanol and acetonitrile as the mobile phases). The majority of the screened selectands, especially those bearing 1-(3-X-benzyl)piperidin-3-yl moieties, showed baseline enantiomer separations, and compound 8 (X = NO2) was the best resolved (α = 2.01; RS = 4.27). Linear free-energy relationships, usefully complemented by molecular docking calculations, proved the key role in enantioselective retention of aromatic interactions between π-donor moieties in the chiral selector and π-acceptor moieties in selectand, strengthened by hydrogen bond interaction between a hydrogen bond donor in the chiral selector and the hydrogen bond acceptor group(s) in the selectand. Statistically reliable equations highlighted the importance of the substituent's size and substitution pattern (meta better than para) to affect the enantiorecognition of the title compounds. The chromatographic data support the scalability of the optimized experimental conditions for preparative purposes. This article is protected by copyright. All rights reserved



Simultaneous determination and qualitative analysis of six types of components in Naoxintong capsule by miniaturized matrix solid-phase dispersion extraction coupled with UHPLC with photodiode array detection and Q-TOF-MS

2018-02-03T02:50:32.864082-05:00

A simple and effective sample preparation process based on miniaturized matrix solid-phase dispersion was developed for simultaneous determination of phenolic acids (gallic acid, chlorogenic acid, ferulic acid, 3,5-dicaffeoylqunic acid, 1,5-dicaffeoylqunic acid, rosmarinic acid, lithospermic acid, salvianolic acid B), flavonoids (kaempferol-3-O-rutinoside, calycosin, formononetin), lactones (ligustilide, butyllidephthalide), monoterpenoids (paeoniflorin), phenanthraquinones (cryptotanshinone) and furans (5-hydroxymethylfurfural) in Naoxintong capsule by ultra high performance liquid chromatography. The optimized condition was that 25 mg Naoxintong powders was blended homogeneously with 100 mg Florisil PR for 4 min. One millilitre methanol/water (75:25, v/v) acidified by 0.05% formic acid was selected to elute all components. It was found that the recoveries of the six types of components ranged from 61.36 to 96.94%. The proposed miniaturized matrix solid-phase dispersion coupled with ultra high performance liquid chromatography was successfully applied to simultaneous determination of the six types of components in Naoxintong capsules. The results demonstrated that the proposed miniaturized matrix solid-phase dispersion coupled with ultra high performance liquid chromatography could be used as an environmentally friendly tool for the extraction and determination of multiple bioactive components in natural products. This article is protected by copyright. All rights reserved



Microgradient separation technique for purification and fractionation of permethylated N-glycans before mass spectrometric analyses

2018-02-02T00:50:29.170819-05:00

Analysis of N-glycans released enzymatically from patients’ sera or other clinical samples may provide diagnostically and prognostically important information in human disease. Permethylation of these biomolecules simultaneously increases their hydrophobicity and substantially improves their detection parameters in the following mass spectrometric analyses. The overall procedure, from the glycan cleavage to the final mass spectrometric determinations, includes several steps involving extraction, derivatization and purification. During these steps, certain polymeric contaminants that may have been coincidentally introduced could hamper the final measurements. To understand and counter these interferences and further fractionate or preconcentrate these glycans, we introduce here an effective microgradient chromatographic technique that employs a small reversed-phase microcolumn connected to a gas-tight microsyringe delivering a mobile-phase gradient. After loading the glycan fraction onto the microcolumn, three elution steps are recommended: 1) remove polar contaminants; 2) recover permethylated glycans for either liquid chromatography with electrospray ionization mass spectrometry or matrix-assisted laser desorption/ionization mass spectrometry; and 3) remove larger polymeric contaminants and regenerate the precolumn. We further demonstrate that the trapped second fraction can be beneficially preconcentrated and further separated to achieve matrix-assisted laser desorption/ionization mass spectrometric detection of the derivatized N-glycans up to 6300 Da. The enhanced detection capabilities for tetra-antennary N-glycans are of increasing interest in disease biomarker discovery. This article is protected by copyright. All rights reserved



Synthesis of molecular imprinted dye-silica nanocomposites with high selectivity and sensitivity: Fluorescent imprinted sensor for rapid and efficient detection of τ-fluvalinate in vodka

2018-02-01T11:25:30.845599-05:00

An imprinted fluorescent sensor was fabricated based on SiO2 nanoparticles encapsulated with molecular imprinted polymer containing allyl fluorescein. High fluorine cypermethirin as template molecules, methyl methacrylate as functional monomer, and allyl fluorescein as optical materials synthesized a core-shell fluorescent molecular imprinted sensor, which showed a high and rapid sensitivity and selectivity for the detection of τ-fluvalinate. The sensor presented appreciable sensitivity with a limit of 13.251 nM, rapid detection that reached to equilibrium within 3 min, great linear relationship in the relevant concentration range from 0 to 150 nM and excellent selectivity over structural analogues. In addition, the fluorescent sensor demonstrated desirable regeneration ability (eight cycling operation). The molecular imprinted polymers ensured specificity, while the fluorescent dyes provided the stabile sensitivity. Finally, an effective application of the sensor was implemented by the detection of τ-fluvalinate in real samples from vodka. The molecular imprinted fluorescent sensor showed a promising potential in environmental monitoring and food safety. This article is protected by copyright. All rights reserved



Rapid characterization of chemical constituents and metabolites of Qi-Jing-Sheng-Bai granule by using UHPLC–Q-TOF-MS

2018-01-31T12:04:43.349169-05:00

Qi-Jing-Sheng-Bai granule is an effective traditional Chinese medicine formula that has been widely used for the treatment of leukopenia post radiotherapy or chemotherapy. However, its chemical constituents were still unclear, which hindered interpreting bioactive constituents and studying integrative mechanisms. In this study, we developed a three-step strategy to characterize the chemical constituents and metabolites of Qi-Jing-Sheng-Bai by using ultra high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. As a result, a total of 143 compounds, including 56 flavonoids, 51 saponins and 36 other compounds, of which contained six pairs of isomers, were tentatively identified or characterized via reference standards and by comparing mass spectrometry data with literature. After oral administration of 15 g/kg Qi-Jing-Sheng-Bai, a number of 42 compounds including 24 prototype compounds and 18 metabolites have been detected in the serum of rats. This work serves the first reference for Qi-Jing-Sheng-Bai chemical components and metabolites. Moreover, it provided a rapid and valid analytical strategy for characterization of the chemical compounds and metabolites of traditional Chinese medicine formula. This article is protected by copyright. All rights reserved



Photografted methacrylate-based monolithic columns coated with cellulose tris(3,5-dimethylphenylcarbamate) for chiral separation in CEC

2018-01-31T12:04:27.551545-05:00

A chiral capillary monolithic column for enantiomer separation in capillary electrochromatography was prepared by coating cellulose tris(3,5-dimethylphenylcarbamate) on porous glycidyl methacrylate-co-ethylene dimethacrylate monolith in capillary format grafted with chains of [2(methacryloyloxy)ethyl] trimethylammonium chloride. The surface modification of the monolith by the photografting of [2(methacryloyloxy)ethyl] trimethylammonium chloride monomer as well as the coating conditions of cellulose tris(3,5-dimethylphenylcarbamate) onto the grafted monolithic scaffold were optimized to obtain a stable and reproducible chiral stationary phase for capillary electrochromatography. The effect of organic modifier (acetonitrile) in aqueous mobile phase for the enantiomer separation by capillary electrochromatography was also investigated. Several pairs of enantiomers including acidic, neutral, and basic analytes were tested and most of them were partially or completely resolved under aqueous mobile phases. The prepared monolithic chiral stationary phases exhibited a good stability, repeatability, and column-to-column reproducibility, with relative standard deviations below 11% in the studied electrochromatographic parameters. This article is protected by copyright. All rights reserved



Preparative isolation and purification of hainanmurpanin, meranzin, and phebalosin from leaves of Murraya exotica L. using supercritical fluid extraction combined with consecutive high-speed countercurrent chromatography

2018-01-31T11:58:57.000726-05:00

The objective of this study was to develop a consecutive preparation method for the isolation and purification of hainanmurpanin, meranzin and phebalosin from leaves of Murraya exotica L. The process involved supercritical fluid extraction with CO2, solvent extraction and two-step high-speed countercurrent chromatography. Pressure, temperature and the volume of entrainer were optimized as 27 MPa, 52°C and 60 mL by response surface methodology in supercritical fluid extraction with CO2, and the yield of the crude extracts was 7.91 g from 100 g of leaves. Subsequently, 80% methanol/water was used to extract and condense the three compounds from the crude extracts, and 4.23 g of methanol/water extracts was obtained. Then, a two-step HSCCC procedure was developed for the isolation of the three target compounds from methanol/water extracts, including conventional high-speed countercurrent chromatography for further enrichment and consecutive high-speed countercurrent chromatography for purification. The yield of concentrates from high-speed countercurrent chromatography was 2.50 g from 4.23 g of methanol/water extracts. Finally, the consecutive high-speed countercurrent chromatography produced 103.2 mg of hainanmurpanin, 244.7 mg of meranzin and 255.4 mg of phebalosin with purities up to 97.66, 99.36 and 98.64%, respectively, from 900 mg of HSCCC concentrates in one run of three consecutive sample loadings without exchanging a solvent system. This article is protected by copyright. All rights reserved



Magnetic separation coupled with HPLC−MS for the rapid separation and determination of lignans in Schisandra Chinensis

2018-01-31T03:22:04.166637-05:00

Despite the strong antihepatotoxic, antioxidant, and antitumor properties of lignans in Schisandra chinensis, their applications in new drug development, bioscience and functional foods etc. are limited because of their low abundance and complex co-extractions. In this study, a magnetic separation method has been developed based on the polyethylenimine modified magnetic nanoparticles to rapidly and effectively separate and purify the lignans from Schisandra chinensis crude extracts through cation–π interaction and electrostatic adsorption. The magnetic nanoparticles were characterized by transmission electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy and X-ray diffraction. Polyethylenimine-modified magnetic nanoparticles showed a spherical-shaped morphology and the average size was about 10 nm with superparamagnetism. Under the pH 7.4, polyethylenimine modified magnetic nanoparticles can remove a lot of co-extracts. The range of detection limits and quantification limits were 0.27–0.34 and 0.89–1.13 ng mL−1, respectively. Compared with other common methods, the magnetic separation method proposed in this study is much simpler, and more effective through both strong cation–π interaction and electrostatic interaction. This article is protected by copyright. All rights reserved



Modeling and predicting chiral stationary phase enantioselectivity: An efficient random forest classifier using an optimally balanced training dataset and an aggregation strategy

2018-01-30T22:20:26.772434-05:00

Predicting whether a chiral column will be effective is a daily task for many analysts. Moreover, finding the best chiral column for separating a particular racemic compound is mostly a matter of trial and error that may take up to week in some cases. In this study we have developed a novel prediction approach based on combining a random forest classifier and an optimized discretization method for dealing with enantioselectivity as a continuous variable. Using the optimization results, models were trained on data sets divided into four enantioselectivity classes. The best model performances were achieved by over-sampling the minority classes (α ≤ 1.10 and α ≥ 2.00), down-sampling the majority class (1.2 ≤ α < 2.0) and aggregating multicategory predictions into binary classifications. We tested our method on 41 chiral stationary phases using layered fingerprints as descriptors. Experimental results show that this learning methodology was successful in terms of average area under the receiver operating characteristic curve, Kappa indices and F-measure for structure-based prediction of the enantioselective behavior of 34 chiral columns. This article is protected by copyright. All rights reserved



Automated solid-phase extraction of Phenolic Acids using layered double hydroxide-alumina-polymer disks

2018-01-26T10:51:50.136761-05:00

The application of layered double hydroxide-Al2O3-polymer mixed-matrix disks for solid-phase extraction is reported for the first time. Al2O3 is embedded in a polymer matrix followed by an in situ metal-exchange process to obtain a layered double hydroxide-Al2O3-mixed-matrix disk with excellent flow-through properties. The extraction performance of the prepared disks is evaluated as proof of concept for the automated extraction using sequential injection analysis of organic acids (p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, gallic acid) following an anion-exchange mechanism. After solid-phase extraction, phenolic acids were quantified by reversed-phase HPLC with diode-array detection using a core-shell silica-C18 stationary phase and isocratic elution (acetonitrile/0.5% acetic acid in pure water, 5:95, v/v). High sensitivity and reproducibility were obtained with limits of detection in the range of 0.12–0.25 μg L−1 (sample volume, 4 mL), and RSDs between 2.9–3.4 % (10 μg L−1, n = 6). Enrichment factors of 34–39 were obtained. Layered double hydroxide-Al2O3-mixed-matrix disks had an average lifetime of 50 extractions. Analyte recoveries ranged from 93 to 96% for grape juice and non-alcoholic beer samples. This article is protected by copyright. All rights reserved



Quantification, dissipation behavior and risk assessment of Ethion in green pea by gas chromatography-electron capture detector

2018-01-26T10:51:09.213856-05:00

Residue investigation was carried out to scrutinize the persistence, dissipation behavior, half life, and risk assessment of ethion on green pea fruit by spraying ethion at the fruiting stage followed by another application at 10 day intervals. The samples were extracted by using the quick, easy, cheap, effective, rugged, and safe method, and the residues of ethion were analyzed by gas chromatography with electron capture detection. Herein we report a novel, accurate and cost-effective gas chromatography method for the determination of average deposits of ethion on green pea. The initial deposits were found to be 4.65 mg kg−1 following the application of insecticide. Residues of ethion reached below detection limit of 0.10 mg kg−1 after 25 days at recommended dosage. The half-life of ethion was found to be 4.62 days. For risk assessment studies, the 25th day will be safe for consumers for consumption of green pea. The developed method is simple, sensitive, selective and repeatable and can be extended for ethion based standardization of herbal formulations containing green pea and its use in pesticide industries. This article is protected by copyright. All rights reserved



Magnetic core micelles as a nanosorbent for the efficient removal and recovery of three organophosphorus pesticides from fruit juice and environmental water samples

2018-01-26T10:20:34.711303-05:00

Sodium dodecyl sulfate coated amino-functionalized magnetic iron oxide nanoparticles were used as an efficient adsorbent for rapid removal and preconcentration of three important organophosphorus pesticides, Chlorpyrifos, Diazinon and Phosalone, by ultrasound-assisted dispersive magnetic solid-phase microextraction. Fabrication of amino-functionalized magnetic nanoparticles was certified by characteristic analyses, including: FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. Affecting parameters on the removal efficiency were investigated and optimized through half fractional factorial design and Doehlert design, respectively. The analysis of analytes was performed by high-performance liquid chromatography with UV detection. Under the optimum conditions, extraction recoveries for 20 ng/mL of organophosphorus pesticides were in the range of 84–97% with preconcentration factors in the range of 134–155. Replicating the experiment in above condition for five times, gave the relative standard deviations lower than 6%. The calibration curves showed high linearity in the range of 0.2–700 ng/mL and the limits of detection were in the range of 0.08–0.13 ng/mL. The proposed method was successfully applied for both removal and trace determination of these three organophosphorus pesticides in environmental water and fruit juice samples. This article is protected by copyright. All rights reserved



Silicon carbide nanomaterial as a coating for solid-phase microextraction

2018-01-26T05:50:20.380908-05:00

Silicon carbide has excellent properties, such as corrosion resistance, high strength, oxidation resistance, high temperature and so on. Based on these, silicon carbide was coated on the stainless steel wire and used as a solid-phase microextraction coating, and the polycyclic aromatic hydrocarbons was employed as model analytes. Using gas chromatography, some important factors that affect the extraction efficiency were optimized one by one, and an analytical method was established. The analytical method shown wide linear ranges (0.1–30, 0.03–30 and 0.01–30 μg L−1) with satisfactory correlation coefficients (0.9922–0.9966) and low detection limits (0.003–0.03 μg L−1). To investigate the practical application of the method, rainwater and cigarette ash aqueous solution were collected as real samples for extraction and detection. The results indicate that silicon carbide has excellent application in the field of solid-phase microextraction. This article is protected by copyright. All rights reserved



Efficient analysis of phytochemical constituents in the peel of Chinese wild Citrus Mangshanju (Citrus reticulata Blanco) by UHPLC–Q-TOF-MS

2018-01-25T12:21:15.599154-05:00

An efficient ultra high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was developed for separation and profiling of phytochemical constituents of Chinese wild mandarin, Mangshanju (Citrus reticulata Blanco). All constituents were well separated within 16 min. Based on retention times, accurate mass, MSE fragments and/or reference standards as well as databases, a total of 81 compounds were unambiguously identified or tentatively assigned including flavonoid glycosides, acylated flavonoid glycosides, flavones, polymethoxylated flavonoids and limonoids as well as four other compounds. Among them, 22 polymethoxylated flavones and 10 polymethoxylated flavanones/chalcones were identified in Mangshanju, more types than other citrus reported before. A basic procedure for identifying flavonoid-O-glycosides and the aglycones including polymethoxylated flavonoids was proposed. In addition, this method was successfully used to analyze another four mandarin germplasms, Cenxi suan ju, Xipi gousi gan, Nanfeng miju and Or, showing that Mangshanju contained two characteristic compounds distinct from the other four citrus species. This study systematically profiled phytochemical constituents of Mangshanju, which was helpful for further utilization of Mangshanju owing to its abundant bioactive compounds. This article is protected by copyright. All rights reserved



Carrier-Ampholyte-free Isoelectric Focusing on a Paper-based Analytical Device for the Fractionation of Proteins

2018-01-25T12:21:01.598114-05:00

Isoelectric focusing plays critical role in the analysis of complex protein samples. Conventionally, isoelectric focusing is implemented with carrier ampholytes in capillary or immobilized pH gradient gel. In this study, we successfully exhibited a carrier ampholyte free isoelectric focusing on paper based analytical device. Proof of concept was visually demonstrated with color model proteins. Experimental results showed that not only a pH gradient was well established along the open paper fluidic channel as confirmed by pH indicator strip, the pH gradient range could also be tuned by the catholyte or anolyte. Furthermore, the isoelectric focusing fractions from the paper channel can be directly cut and recovered into solutions for post analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. This paper-based isoelectric focusing method is fast, cheap, simple and easy to operate, and could potentially be used as a cost-effective protein sample clean-up method for target protein analysis with mass spectrometry. This article is protected by copyright. All rights reserved



Analyzing multiple pesticides in tobacco leaf using gas chromatography with quadrupole time-of-flight mass spectrometry

2018-01-25T07:50:22.673236-05:00

A method combining gas chromatography with quadrupole time-of-flight mass spectrometry has been developed for the simultaneous analysis of multiple pesticide residues in tobacco leaf. The retention index and high accurate masses of ions from the first-stage and the second-stage mass spectra of each pesticide were collected for qualitation and quantification. A total of 115 pesticides were evaluated. The extract from organic tobacco leaf was used as a model matrix. The limit of detection was lower than 10 ng/mL, and the limit of quantification was in the range of 1–20 ng/mL for 95% of the tested pesticides. The correlation coefficients were higher than 0.9900 for all tested pesticides. At three concentrations (10, 50, and 100 ng/mL), most compounds presented satisfactory recoveries ranging from 70 to 120% and good precision below 20%. Finally, three tobacco leaf samples collected from a local market were analyzed. A total of three pesticides were found, including dimethachlon, triadimenol and flumetralin. Each pesticide was confirmed by the presence of three m/z ions at the expected retention index and mass. In conclusion, gas chromatography with quadrupole time-of-flight mass spectrometry appears to be one of the most efficient tools for the analysis of pesticide residues in tobacco leaf. This article is protected by copyright. All rights reserved



Preparation of iron-based MIL-101 functionalized polydopamine@Fe3O4 magnetic composites for extracting sulfonylurea herbicides from environmental water and vegetable samples

2018-01-25T05:50:27.314433-05:00

Here, we describe a simple one-pot solvothermal method for synthesizing MIL-101(Fe)@polydopamine@Fe3O4 composites from polydopamine-modified Fe3O4 particles. The composite was used as a magnetic adsorbent to rapidly extract sulfonylurea herbicides. The herbicides were then analyzed by high-performance liquid chromatography. The best possible extraction efficiencies were achieved by optimizing the most important extraction parameters, including desorption conditions, extraction time, adsorbent dose, salt concentration, and the pH of the solution. Good linearity was found (correlation coefficients > 0.9991) over the herbicide concentration range 1–150 μg L−1 using the optimal conditions. The limits of detection (the concentrations giving signal/noise ratios of 3) were low, at 0.12–0.34 μg L−1, and repeatability was good (the relative standard deviations were < 4.8%, n = 6). The method was used successfully to determine four sulfonylurea herbicides in environmental water and vegetable samples, giving satisfactory recoveries of 87.1–108.9%. The extraction efficiency achieved using MIL-101(Fe)@polydopamine@Fe3O4 was compared with the extraction efficiencies achieved using other magnetic composites (polydopamine@Fe3O4, Hong Kong University of Science and Technology (HKUST)-1@polydopamine@Fe3O4, and MIL-100(Fe)@polydopamine@Fe3O4). The results showed that the magnetic MIL-101(Fe)@polydopamine@Fe3O4 composites have great potential for the extraction of trace sulfonylurea herbicides from various sample types. This article is protected by copyright. All rights reserved



Fabrication of an ionic-liquid-based polymer monolithic column and its application in the fractionation of proteins from complex biosamples

2018-01-24T23:51:18.967129-05:00

An ionic-liquid-based polymer monolithic column was synthesized by free-radical polymerization within the confines of a stainless-steel column (50 mm × 4.6 mm i.d.). In the processes, ionic liquid and stearyl methacrylate were used as dual monomers, ethylene glycol dimethacrylate as the cross-linking agent, and polyethylene glycol 200 and isopropanol as co-porogens. Effects of the pre-polymerization solution components on the properties of the resulting monoliths were studied in detail. Scanning electron microscopy, nitrogen adsorption–desorption measurements, and mercury intrusion porosimetry were used to investigate the morphology and pore size distribution of the prepared monoliths, which showed that the homemade ionic-liquid-based monolith column possessed a relatively uniform macro-pore structure with a total macropore specific surface area of 44.72 m2 g−1. Compared to a non-ionic-liquid-based monolith prepared under the same conditions, the ionic-liquid-based monolith exhibited excellent selectivity and high performance for separating proteins from complex bio-samples, such as egg white, snailase, BSA digest solution, human plasma, etc, indicating promising applications in the fractionation and analysis of proteins from the complex bio-samples in proteomics research. This article is protected by copyright. All rights reserved



Effect of different immobilization strategies on chiral recognition properties of Cinchona-based anion exchangers

2018-01-24T11:25:33.5379-05:00

In the enantiomeric separation of highly polar compounds, a traditionally challenging task for high-performance liquid chromatography, ion-exchange chiral stationary phases have found the main field of application. In this contribution, we present a series of novel anion-exchange-type chiral stationary phases for enantiomer separation of protected amino phosphonates and N-protected amino acids. Two of the prepared selectors possessed a double and triple bond within a single molecule. Thus, they were immobilized onto silica support employing either a thiol-ene (radical) or an azide-yne (copper(I) catalyzed) click-reaction. We evaluated the selectivity and the effect of immobilization proceeding either by the double bond of the cinchona alkaloid or a triple bond of the carbamoyl moiety on the chromatographic performance of the chiral stationary phases using analytes with protecting groups of different size, flexibility and π-acidity. The previously observed preference towards protecting groups possessing π-acidic units, which is a typical feature of cinchona-based chiral stationary phases, was preserved. In addition, increasing bulkiness of the selectors’ carbamoyl units leads to significantly reduced retention times, while very high selectivity towards the tested analytes is retained. This article is protected by copyright. All rights reserved



Simultaneous analysis of tropane alkaloids in teas and herbal teas by liquid chromatography coupled to high-resolution mass spectrometry (Orbitrap)

2018-01-23T02:20:57.826796-05:00

A new method has been developed for the simultaneous determination of 13 tropane alkaloids in tea and herbal teas using high-performance liquid chromatography coupled to an Exactive-Orbitrap analyzer. A mixture of methanol, water and formic acid was used for the extraction of the target compounds, followed by a solid-phase extraction step. The validated method provided recoveries from 75 to 128% with intra- and interday precision lower than or equal to 24% (except for apoatropine). Limits of quantification ranged from 5 to 20 μg/kg. Eleven tea and herbal tea samples and two contaminated samples with Datura stramonium seeds were analyzed. Tropane alkaloids were detected in six samples with concentrations from 5 (apoatropine) to 4340 μg/kg (sum of physoperuvine, pseudotropine and tropine), whereas concentrations from 5 (apoatropine) to 1725 μg/kg (sum of physoperuvine, pseudotropine and tropine) were found in the contaminated samples. This article is protected by copyright. All rights reserved



Impact of column and stationary phase properties on the productivity in chiral preparative LC

2018-01-22T22:50:30.870253-05:00

By generating 1500 random chiral separation systems, assuming two-site Langmuir interactions, we investigated numerically how the maximal productivity (PR,max) was affected by changes in stationary phase adsorption properties. The relative change in PR,max, when one adsorption property changed 10%, was determined for each system and for each studied parameter the corresponding productivity change distribution for the systems were analyzed. We could conclude there is no reason to have columns with more than 500 theoretical plates and larger selectivity than 3. More specifically, we found that changes in selectivity have major impact on PR,max if it is below ∼2 and, interestingly, increasing selectivity when it is above ∼3 decreases PR,max. Increases in relative saturation capacity will have major impact on PR,max if it is below ∼40%, but only modest above. Increasing total monolayer saturation capacity, or decreasing the first eluting enantiomer's retention factor, will have modest effect on PR,max and increased efficiency will have almost no effect at all on PR,max unless it is below ∼500 theoretical plates. Finally, we showed that chiral columns with superior analytic performance might have inferior preparative performance, or vice versa, it is, therefore, not possible to scout columns based on their analytic performance alone. This article is protected by copyright. All rights reserved



Fabrication of magnetic zinc adeninate metal–organic frameworks for the extraction of benzodiazepines from urine and wastewater

2018-01-22T06:20:47.834966-05:00

In this study, an alternative method for synthesizing magnetic cobalt adeninate metal–organic frameworks was developed, and the synthesized materials were examined for their potential application for separating and enriching benzodiazepines from complex samples. Benzodiazepines, widely used as hypnotics, muscle relaxants, sedatives, and anxiolytics, are a class of drugs that require being accurately detected and monitored. Results showed that Fe3O4 nanoparticles could be well anchored onto the external surface of cobalt adeninate metal–organic frameworks by using amino-silane as a linkage. Their adsorption of benzodiazepines was mainly promoted by intermolecular hydrogen binding, π–π interaction and electrostatic attraction. Their potential application was evaluated by extraction of benzodiazepines in urine and wastewater samples prior to liquid chromatography with mass spectrometry. Under optimum conditions, the calibration curves were linear with a correlation coefficient of ≥ 0.9928 in the concentration range of 10–5000 ng/L for lorazepam and 5–5000 ng/L for estazolam, chlordiazepoxide, alprazolam, midazolam and triazolam. The limits of detection were in the range of 0.71–2.49 ng/L. The percent of extraction recoveries were 80.2–94.5% for urine and 84.1–94.4% for wastewater, respectively. Results suggested that magnetic cobalt adeninate metal–organic frameworks could potentially be a promising material for enriching benzodiazepines from urine and wastewater with high accuracy and precision. This article is protected by copyright. All rights reserved



Simultaneous extraction and determination of trace amounts of diclofenac from whole blood using supported liquid membrane microextraction and fast fourier transform voltammetry

2018-01-19T08:20:37.819702-05:00

A novel, simple and inexpensive analytical technique based on flat sheet supported liquid membrane microextraction coupled with fast Fourier transform stripping cyclic voltammetry on a reduced graphene oxide carbon paste electrode was used for the extraction and online determination of diclofenac in whole blood. First, diclofenac was extracted from blood samples using a polytetrafluoroethylene membrane impregnated with 1-octanol and then into an acceptor solution, subsequently it was oxidized on a carbon paste electrode modified with reduced graphene oxide nano-sheets. The optimal values of the key parameters influencing the method were; scan rate = 6 V s−1, stripping potential = 200 mV, stripping time = 5 s, pH of the sample solution = 5, pH of the acceptor solution = 7, and extraction time = 240 min. The calibration curves were plotted for the whole blood samples and the method was found to have a good linearity within the range of 1–25 μg mL–1 with a determination coefficient of 0.99. The limits of detection and quantification were 0.1 and 1.0 μg mL−1, respectively. Using this coupled method, the extraction and determination were merged into one step. Accordingly, the speed of detection for sensitive determination of diclofenac in complex samples like blood increased considerably. This article is protected by copyright. All rights reserved



Simultaneous pharmacokinetics and stability studies of physalins in rat plasma and intestinal bacteria culture media using liquid chromatography with mass spectrometry

2018-01-13T06:50:21.144924-05:00

Physalins are the major steroidal constituent of Physalis plants and display a range of biological activity. For this study, a rapid and sensitive high-performance liquid chromatography with triple quadrupole mass spectrometry method was developed for the simultaneous quantification of six physalins. Specifically, it was for the quantification of physalin A, physalin B, physalin D, physalin G, 4,7-didehydroneophysalin B and isophysalin B in rat plasma and rat intestinal bacteria. After a solid-phase extraction, analytes and internal standards (prednisolone) were separated on a Shield reverse-phase C18 column (measuring 3 mm × 150 mm with an internal diameter of 3.5 μm) and determined using multiple reactions in a monitoring mode with a positive-ion electrospray ionization source. The mobile phase was a mix of 0.1% formic acid in water (A) and acetonitrile (B) and was used at a flow rate of 0.6 mL/min. The intra- and inter-day precisions were within 15% with accuracies ranging from 86.2–114%. The method was validated and successfully applied to pharmacokinetics and stability studies of six physalins in rat plasma and rat intestinal bacteria, respectively. The results showed that physalin B and isophysalin B could not be absorbed by rats, and rat intestinal bacteria could quickly transform physalins. This article is protected by copyright. All rights reserved



Metal–organic framework based in-syringe solid-phase extraction for the on-site sampling of polycyclic aromatic hydrocarbons from environmental water samples

2018-01-13T01:20:27.817617-05:00

In-syringe solid-phase extraction is a promising sample pretreatment method for the on-site sampling of water samples because of its outstanding advantages of portability, simple operation, short extraction time and low cost. In this work, a novel in-syringe solid-phase extraction device using metal–organic frameworks as the adsorbent was fabricated for the on-site sampling of polycyclic aromatic hydrocarbons from environmental waters. Trace polycyclic aromatic hydrocarbons were effectively extracted through the self-made device followed by gas chromatography with mass spectrometry analysis. Owing to the excellent adsorption performance of metal–organic frameworks, the analytes could be completely adsorbed during one adsorption cycle, thus effectively shortening the extraction time. Moreover, the adsorbed analytes could remain stable on the device for at least 7 days, revealing the potential of the self-made device for on-site sampling of degradable compounds in remote regions. The limit of detection ranged from 0.20 to 1.9 ng L−1 under the optimum conditions. Satisfactory recoveries varying from 84.4 to 104.5% and relative standard deviations below 9.7% were obtained in real samples analysis. The results of this study promote the application of metal–organic frameworks in sample preparation and demonstrate the great potential of in-syringe solid-phase extraction for the on-site sampling of trace contaminants in environmental waters. This article is protected by copyright. All rights reserved



Determination of major aromatic constituents in vanilla using on-line supercritical fluid extraction coupled with supercritical fluid chromatography

2017-12-28T01:50:23.471644-05:00

An on-line supercritical fluid extraction coupled with supercritical fluid chromatography method was developed for the determination of four major aromatic constituents in vanilla. The parameters of supercritical fluid extraction were systematically investigated using single factor optimization experiments and response surface methodology by a Box–Behnken Design. The modifier ratio, split ratio and the extraction temperature and pressure were the major parameters which have significant effects on the extraction. While the static extraction time, dynamic extraction time and recycle time had little influences on the compounds with low polarity. Under the optimized conditions, the relative extraction efficiencies of all the constituents reached 89.0–95.1%. The limits of quantification were in the range of 1.123–4.747 μg. The limits of detection were in the range of 0.3368–1.424 μg. The recoveries of the four analytes were in the range of 76.1–88.9%. The relative standard deviations of intra-day and inter-day precision ranged from 4.2 to 7.6%. Compared with other off-line methods, the present method obtained higher extraction yields for all four aromatic constituents. Finally, this method has been applied to the analysis of vanilla from different sources. On the basis of the results, the on-line supercritical fluid extraction-supercritical fluid chromatography method shows great promise in the analysis of aromatic constituents in natural products. This article is protected by copyright. All rights reserved



Separation of enantiomers of New Psychoactive Substances by HPLC

2017-12-27T01:51:11.242633-05:00

New psychoactive substances are defined as compounds with consciousness-changing effects and have been developed simultaneously with classical drugs. They arise through structural modifications of illegal substances and are mainly produced to circumvent laws. Availability is simple, since new psychoactive substances can be purchased from the Internet. Among them many chemical drug compound classes are chiral and thus the two resulting enantiomers can differ in their effect. The aim of this study was to develop a suitable chiral high-performance liquid chromatography separation method for a broad spectrum of new psychoactive substances using cellulose tris(3,5-dichlorophenylcarbamate) as a chiral selector. Experiments were performed by high-performance liquid chromatography in normal-phase mode under isocratic conditions using ultraviolet detection. Direct separation was carried out on a high-performance liquid chromatography column (Lux® i-cellulose-5, 3.5 μm, Phenomenex®), available since 2016. Excellent separation results were obtained for cathinones. After further optimization, even 47 instead of 39 out of 52 cathinones showed baseline separation. For amphetamine derivatives, satisfactory results were not achieved. Further New Psychoactive Substances from other compound classes such as benzofuranes, thiophenes, phenidines, phenidates, morpholines and ketamines were partially resolved, dependent on the polarity and degree of substitution. All analytes, which were mainly purchased from the Internet were proven to be traded as racemates. This article is protected by copyright. All rights reserved



Electroless-coated magnetic three-dimensional graphene with silver nanoparticles used for the determination of pesticides in fruit samples

2017-12-12T03:04:42.697513-05:00

A new type of adsorbent composed of magnetic three-dimensional graphene coated with silver nanoparticles was synthesized by an electroless technique and used in the magnetic solid-phase extraction of selected pesticides (fenitrothion, chlorpyrifos, and hexaconazole) before gas chromatography with micro-electron capture detector. The adsorbent was characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry and field-emission scanning electron microscopy. The important extraction parameters such as pH, adsorbent dose, extraction time and desorption conditions were investigated. Under the optimal conditions, the analytical figures of merit were obtained as: linear dynamic range of 0.1–5 ng g−1 with determination coefficients of 0.991–0.996; limit of detection of 0.07–0.13 ng g−1; limit of quantification of 0.242–0.448 ng g−1; and the intra-day and inter-day relative standard deviations (C = 5 ng g−1, n = 3) were 3.8–8.7 and 6.6–8.9%, respectively. The developed method was successfully applied for analysis of the selected pesticides in tomato and grape with extraction recoveries in the range of 72.8–109.6%. This article is protected by copyright. All rights reserved



Rapid determination of catecholamines in urine samples by nonaqueous microchip electrophoresis with LIF detection

2013-08-14T04:35:17.286562-05:00

A method was developed for the rapid separation of catecholamines by nonaqueous microchip electrophoresis with LIF detection, A homemade pump-free negative pressure sampling device was used for rapid bias-free sampling in nonaqueous microchip electrophoresis, the injection time was 0.5 s and the electrophoresis separation conditions were optimized. Under the optimized conditions, the samples were separated completely in less than 1 min. The average migration times of the epinephrine, dopamine, and norepinephrine were 34.26, 43.81, and 50.07 s, with a relative standard deviation of 1.05, 1.26 and 0.89% (n = 7), respectively. The linearity of the method ranged from 0.0125 to 2.0 mg/L for epinephrine and 0.025∼4.0 mg/L for dopamine, and norepinephrine, with correlation coefficients ranging between 0.9978 and 0.9986. The detection limits of epinephrine, dopamine, and norepinephrine were 2.5, 5.0 and 5.0 μg/L, respectively. The recoveries of epinephrine, dopamine, and norepinephrine in spiked urine samples were between 86 and 103%, with relative standard deviations of 4.5∼6.8% (n = 5). The proposed nonaqueous microchip electrophoresis with laser induced fluorescence detection system combined with a pump-free negative pressure sampling device was a simple, inexpensive, energy efficient, miniaturized system that can be successfully applied for the determination of catecholamines in urine samples. This article is protected by copyright. All rights reserved



Development and validation of a stability-indicating HPLC method for topiramate using a mixed-mode column and charged aerosol detector

2018-02-20T09:11:34.921311-05:00

The analysis of topiramate in the presence of its main degradation products is challenging due to the absence of chromophore moieties and their wide range of polarity. Mixed-mode chromatography has been used in such cases because it combines two or more modes of separation. Charged aerosol detector is also an alternative since its detection is independent of optical properties and analyte ionization. This study is aimed to develop and validate two new stability-indicating methods by high-performance liquid chromatography for the main degradation products of topiramate using mixed-mode chromatography and a charged aerosol detector. Method 1 employed an Acclaim Trinity P1® column (3.0 mm × 150 mm, 2.7 μm) with a mobile phase comprising of 80% ammonium acetate buffer (20 mM, pH 4.0) and 20% methanol at a flow rate of 0.5 mL/min at 35°C. Method 2 utilized a C18 Acclaim 120® column (4.6 mm × 250 mm; 5 μm) with ACN/water (50:50) at a flow rate of 0.6 mL/min at 50°C. Validation of the two methods demonstrated excellent performance with respect to linearity, precision, accuracy, and selectivity. The limits of detection for topiramate, fructose, sulfate, sulfamate, and compound A were 2.97, 12.08, 4.02, 13.91, and 3.94 μg/mL, respectively.



Enantiomeric separation of six chiral pesticides that contain chiral sulfur/phosphorus atoms by supercritical fluid chromatography

2018-02-20T09:05:57.848847-05:00

Six chiral pesticides containing chiral sulfur/phosphorus atoms were separated by supercritical fluid chromatography with supercritical CO2 as the main mobile phase component. The effect of the chiral stationary phase, different type and concentration of modifiers, column temperature, and backpressure on the separation efficiency was investigated to obtain the appropriate separation condition. Five chiral pesticides (isofenphos-methyl, isocarbophos, flufiprole, fipronil, and ethiprole) were baseline separated under experimental conditions, while isofenphos only obtained partial separation. The Chiralpak AD-3 column showed a better chiral separation ability than others for chiral pesticides containing chiral sulfur/phosphorus atoms. When different modifiers at the same concentration were used, the retention factor of pesticides except flufiprole decreased in the order of isopropanol, ethanol, methanol; meanwhile, the retention factor of flufiprole increased in the order of isopropanol, ethanol, methanol. For a given modifier, the retention factor and resolution decreased on the whole with the increase of its concentration. The enantiomer separation of five chiral pesticides was an “enthalpy-driven” process, and the separation factor decreased as the temperature increased. The backpressure of the mobile phase had little effect on the separation factor and resolution.



Ultra-performance convergence chromatography method for the determination of four chromones and quality control of Saposhnikovia divaricata (Turcz.) Schischk.

2018-02-20T09:05:43.247388-05:00

Ultra-performance convergence chromatography is an environmentally friendly analytical technique that employs dramatically reduced amounts of organic solvents compared to conventional chromatographic methods. In this study, a rapid, sensitive, and environmentally friendly method based on ultra-performance convergence chromatography was developed for the quantification of four major chromones present in the roots of Saposhnikovia divaricata (Turcz.) Schischk. Using this method, the analysis time was significantly shortened compared to conventional high-performance liquid chromatography techniques. In addition, the influence of cosolvent type, cosolvent ratio, column temperature, system pressure, and flow rate on the peak resolution was investigated. The proposed method was validated in terms of its limits of detection, limits of quantitation, linearity, precision, and accuracy. More specifically, the limits of detection of the four chromones ranged from 0.006 to 0.033 μg/mL, while the limits of quantitation ranged from 0.019 to 0.101 μg/mL. Our method also exhibited a good regression (r2 > 0.999), excellent precision (RSD < 0.60%), and acceptable recoveries (99.48–102.89%). Finally, the quantities of these four chromones present in 20 commercial samples from Korea and China were successfully evaluated using the developed method, indicating that the proposed method is suitable for the rapid and accurate quality control of Saposhnikovia divaricata.



Simultaneous determination of seven phenylethanoid glycosides in Cistanches Herba by a single marker using a new calculation of relative correction factor

2018-02-12T08:10:29.760948-05:00

Current quantitative analysis of multi-components by a single marker is usually performed by using liquid chromatography methods coupled with ultraviolet or mass spectrometry detection to afford the relative correction factors between reference standard and other components. However, low durability of the relative correction factors caused by different chromatographic system leading this approach lacking a high accuracy. In the present study, a simple but effective method was established by employing the absorption coefficient (E1 cm 1%) to calculate the relative correction factors instead of peak area or height. The absorption coefficient, a fundamental constant of physics, has been widely used for qualitative and quantitative analysis in Pharmacopoeia all over the world. According to the absorbance coefficient ratio between echinacoside and other compounds, the content of seven phenylethanoid glycosides in Cistanche deserticola and Cistanches tubulosa were determined simultaneously. The low standard method difference on quantitative measurement of seven compounds in Cistanches Herba between our method and the external standard method proved the consistency of the two methods. Using an ultra high performance liquid system, these seven bioactive phenylethanoid glycosides were baseline separated in 8 min. All the data suggested that the method was accurate and reliable for the determination of multi-components when authentic standard substances were unavailable.



Extraction and identification of matrine-type alkaloids from Sophora moorcroftiana using double-templated molecularly imprinted polymers with HPLC–MS/MS

2018-02-12T03:26:15.423652-05:00

Double-templated molecularly imprinted polymers with specific recognition of three matrine-type alkaloids were prepared using matrine and oxymatrine as the template molecules. An approach based on double-templated molecularly imprinted solid-phase extraction coupled with high-performance liquid chromatography and tandem mass spectrometry was then developed to extract and purify matrine, oxymatrine, and sophocarpine from Sophora moorcroftiana in the Tibetan plateau herbs. The polymers were characterized by Fourier-transform infrared spectroscopy and scanning electron microscopy. Their adsorption characteristics were evaluated using adsorption kinetics, isotherms, selectivity, and recycling experiments. This polymer exhibited excellent molecular recognition ability and good selectivity. The obtained polymers as adsorbent was further used for the determination of three matrine-type alkaloids coupled to high-performance liquid chromatography with tandem mass spectrometry, the recoveries of three matrines spiked at three concentration levels in samples were 73.25–98.42% (n = 5) with a relative standard deviation less than 6.82%. The limits of detection for the method were 9.23–15.42 μg/kg (S/N = 3). This proposed method was assessed to be an effective method for simultaneous extraction, isolation, and identification of matrine, oxymatrine, and sophocarpine from Sophora moorcroftiana.



Detection of peroxyl radicals from polluted air by free radical reaction combined with liquid chromatography signal amplification technique

2018-02-12T03:20:32.482458-05:00

Free radicals play an important role in the oxidizing power of polluted air, the development of aging-related diseases, the formation of ozone, and the production of secondary particulate matter. The high variability of peroxyl radical concentration has prevented the detection of possible trends or distributions in the concentration of free radicals. We present a new method, free radical reaction combined with liquid chromatography photodiode array detection, for identifying and quantifying peroxyl radicals in polluted air. Functionalized graphene was used for loading peroxyl radicals and reactive molecules in air sampling system, which can facilitate reaction kinetics (charge transfers) between peroxyl radicals and reaction molecules. Separation was performed with and without a preliminary exposure of the polluted air sample to reactive molecule(s) system. The integral chromatographic peak areas before and after air sampling are used to quantify the atmospheric peroxyl radicals in polluted air. The utility of the new technique was tested with measurements carried out in the field.



Rapid profiling of polymeric phenolic acids in Salvia miltiorrhiza by hybrid data-dependent/targeted multistage mass spectrometry acquisition based on expected compounds prediction and fragment ion searching

2018-02-09T08:55:49.546474-05:00

Phenolic acids are the major water-soluble components in Salvia miltiorrhiza (>5%). According to previous studies, many of them contribute to the cardiovascular effects and antioxidant effects of S. miltiorrhiza. Polymeric phenolic acids can be considered as the tanshinol derived metabolites, e.g., dimmers, trimers, and tetramers. A strategy combined with tanshinol-based expected compounds prediction, total ion chromatogram filtering, fragment ion searching, and parent list-based multistage mass spectrometry acquisition by linear trap quadropole-orbitrap Velos mass spectrometry was proposed to rapid profile polymeric phenolic acids in S. miltiorrhiza. More than 480 potential polymeric phenolic acids could be screened out by this strategy. Based on the fragment information obtained by parent list-activated data dependent multistage mass spectrometry acquisition, 190 polymeric phenolic acids were characterized by comparing their mass information with literature data, and 18 of them were firstly detected from S. miltiorrhiza. Seven potential compounds were tentatively characterized as new polymeric phenolic acids from S. miltiorrhiza. This strategy facilitates identification of polymeric phenolic acids in complex matrix with both selectivity and sensitivity, which could be expanded for rapid discovery and identification of compounds from complex matrix.



Separation of three polar compounds from Rheum tanguticum by high-speed countercurrent chromatography with an ethyl acetate/glacial acetic acid/water system

2018-02-09T03:07:16.783709-05:00

The separation of polar compounds by high-speed countercurrent chromatography is still regarded as a challenge. In this study, an efficient strategy for the separation of three polar compounds from Rheum tanguticum has been successfully conducted by using high-speed countercurrent chromatography. X-5 macroporous resin chromatography was used for the fast enrichment of the target compounds. Then, the target fraction was directly introduced into high-speed countercurrent chromatography for separation using ethyl acetate/glacial acetic acid/water (100:1:100, v/v/v) as the solvent system. Consequently, three polar compounds including gallic acid, catechin, and gallic acid 4-O-β-d-(6′-O-galloyl) glucoside were obtained with purities higher than 98%. The results showed glacial acetic acid could be such an appropriate regulator for the ethyl acetate/water system. This study provides a reference for the separation of polar compounds from natural products by high-speed countercurrent chromatography.



Selective enrichment of N-linked glycopeptides and glycans by using a dextran-modified hydrophilic material

2018-02-09T03:07:11.18826-05:00

Glycosylation analysis of proteins from biological sources utilizing mass spectrometry based approaches is challenging due to the relatively low abundance of glycopeptides, the structural diversity of glycans, and the coexisting matrices. In this study, a customized dextran-bonded silica-based stationary phase was introduced for selective enrichment of glycopeptides and glycans from complex biological samples. This material has exhibited superior selectivity and broader glycosylation site coverage over commercial Sepharose in glycoproteomic evaluation. Additionally, the glycomic analysis of fetuin, α1-acid glycoprotein, and human serum N-glycome also indicated the relatively higher sensitivity, selectivity, and glycoform coverage of dextran-bonded silica than that of Sepharose and porous graphitized carbon. Therefore, the dextran-bonded silica is expected to make contributions in the fields of glycoproteomics and glycomics.



Quantification of total cholesterol in human milk by gas chromatography

2018-02-09T03:06:51.986135-05:00

Human milk provides the key nutrients necessary for infant growth and development. The objective of this study was to develop and validate a method to analyze the cholesterol content in liquid human milk samples along lactation. Direct saponification of the sample using ethanolic potassium hydroxide solution under cold conditions was applied and unsaponifiable matter was separated by centrifugation. Cholesterol was converted into its trimethylsilyl ether and the derivative analyzed by gas chromatography coupled with a flame ionization detector. Cholesterol was quantified using epicoprostanol as internal standard. The method is suitable for the determination of cholesterol in only 0.3 g of human milk. It has been validated showing good repeatability (CV(r) < 15%) and intermediate reproducibility (CV(iR) < 15%). The method was used to analyze human milk obtained from five mothers collected at day 30(±3), 60 (±3) and 120 (±3) after delivery. The cholesterol content in human milk slightly decreased from 13.1 mg/100 g at 1 month to 11.3 mg/100 g 120 days after delivery. The method can also be used to determine desmosterol, an intermediate in cholesterol synthesis.



Selective extraction of bisphenol A from water by one-monomer molecularly imprinted magnetic nanoparticles

2018-02-09T03:05:45.932048-05:00

One-monomer molecularly imprinted magnetic nanoparticles were prepared as adsorbents for selective extraction of bisphenol A from water in this study. A single bi-functional monomer was adopted for preparation of the molecularly imprinted polymer, avoiding the tedious trial-and-error optimizations as traditional strategy. Moreover, bisphenol F was used as the dummy template for bisphenol A to avoid the interference from residual template molecules. These nanoparticles showed not only large adsorption capacity and good selectivity to the bisphenol A but also outstanding magnetic response performance. Furthermore, they were successfully used as magnetic solid-phase extraction adsorbents of bisphenol A from various water samples, including tap water, river water, and seawater. The developed method was found to be much more efficient, convenient, and economical for selective extraction of bisphenol A compared with the traditional solid-phase extraction. Separation of these nanoparticles can be easily achieved with an external magnetic field, and the optimized adsorption time was only 15 min. The recoveries of bisphenol A in different water samples ranged from 85.38 to 93.75%, with relative standard deviation lower than 7.47%. These results showed that one-monomer molecularly imprinted magnetic nanoparticles had the potential to be popular adsorbents for selective extraction of pollutants from water.



Determination of phthalate esters in soil using a quick, easy, cheap, effective, rugged, and safe method followed by GC–MS

2018-02-09T03:05:27.276419-05:00

A quick, easy, cheap, effective, rugged, and safe procedure was designed to extract pesticide residues from fruits and vegetables with a high percentage of water. It has not been used extensively for the extraction of phthalate esters from sediments, soils, and sludges. In this work, this procedure was combined with gas chromatography with mass spectrometry to determine 16 selected phthalate esters in soil. The extraction efficiency of the samples was improved by ultrasonic extraction and dissolution of the soil samples in ultra-pure water, which promoted the dispersion of the samples. Furthermore, we have simplified the extraction step and reduced the risk of organic solvent contamination by minimizing the use of organic solvents. Different extraction solvents and clean-up adsorbents were compared to optimize the procedure. Dichloromethane/n-hexane (1:1, v/v) and n-hexane/acetone (1:1, v/v) were selected as the extractants from the six extraction solvents tested. C18/primary secondary amine (1:1, m/m) was selected as the sorbent from the five clean-up adsorbents tested. The recoveries from the spiked soils ranged from 70.00 to 117.90% with relative standard deviation values of 0.67–4.62%. The proposed approach was satisfactorily applied for the determination of phthalate esters in 12 contaminated soil samples.



Preparation and evaluation of a deoxycholic-calix[4]arene hybrid-type receptor as a chiral stationary phase for HPLC

2018-02-09T03:01:11.796449-05:00

We report the synthesis and enantioseparation characteristics of two novel covalently immobilized deoxycholic acid derivatives as chiral stationary phases for high-performance liquid chromatography. In the structure of the first stationary phase, the 3-position of deoxycholic acid is substituted with a 3,5-dinitrophenylcarbamoyl group and the second one has an additional calix[4]arene attached to the carboxylic group of the deoxycholic acid. The chromatographic performance of the stationary phases was evaluated with enantioseparation of N-(3,5-dinitrobenzoyl)-dl-leucine, N-(3,5-dinitrobenzoyl)-dl-valine, omeprazole, diclofop-methyl, dl-mandelic acid and (RS)-pregabalin. Comparison of the performance characteristics of the prepared chiral stationary phases provided evidence for the active involvement of the calix[4]arene unit in the chiral recognition process. Both stationary phases are chemically bonded to the silica and can be used in both normal-phase and reversed-phase modes.



Cyclodextrin-assisted dispersive liquid–liquid microextraction for the preconcentration of carbamazepine and clobazam with subsequent sweeping micellar electrokinetic chromatography

2018-02-09T03:00:26.841627-05:00

A new version of dispersive liquid–liquid microextraction, namely, cyclodextrin-assisted dispersive liquid–liquid microextraction, with subsequent sweeping micellar electrokinetic chromatography has been developed for the preconcentration and sensitive detection of carbamazepine and clobazam. α-Cyclodextrin and chloroform were used as the dispersive agent and extraction solvent, respectively. After the extraction, carbamazepine and clobazam were analyzed using micellar electrokinetic chromatography with ultraviolet detection. The detection sensitivity was further enhanced using the sweeping technique. Under optimal extraction and stacking conditions, the calibration curves of carbamazepine and clobazam were linear over a concentration range of 2.0–200.0 ng/mL. The method detection limits at a signal-to-noise ratio of 3 were 0.6 and 0.5 ng/mL with sensitivity enhancement factors of 3575 and 4675 for carbamazepine and clobazam, respectively. This developed method demonstrated high sensitivity enhancement factors and was successfully applied to the determination of carbamazepine and clobazam in human urine samples. The precision and accuracy for urine samples were less than 4.2 and 6.9%, respectively.



High-capacity protein A affinity chromatography for the fast quantification of antibodies: Two-wavelength detection expands linear range

2018-02-07T06:00:36.775816-05:00

The high-throughput analysis of antibodies from processes can be enhanced when the linear range is expanded and sample preparation is kept to a minimum. We developed a fast chromatography method based on a hexameric variant of staphylococcal protein A immobilized on Toyopearl matrix, TSK 5 PW using two wavelengths. A protocol with 5 min runtime and a single-wavelength detection at 280 nm yielded an upper limit of quantification of 2.10 mg/mL and a lower limit of quantification of 0.06 mg/mL. The optimized method with a runtime of 2 min and two-wavelength detection at 280 and 300 nm allowed us to span a valid concentration range of 0.01–5.20 mg/mL using two calibration curves. Sample selectivity was tested using mock supernatant mixed with antibody concentrations of 0.1–2.1 mg/mL, sample stability in the autosampler was shown for at least 24 h. We also tested the capabilities of the method to determine purity of an antibody sample by calculating the ratio of peak area of elution to peak area of flow-through, which correlated well with the expected purity. The method will be very useful for process development and in-process control, spanning concentrations from seed fermentation to harvest and purification.



Development and validation of an analytical method for multiresidue determination of pesticides in lettuce using QuEChERS–UHPLC–MS/MS

2018-02-07T06:00:29.883835-05:00

A new analytical method for multiresidue determination of 16 multiclass pesticides in lettuce was developed using ultra-high performance liquid chromatography with tandem mass spectrometry with a triple quadrupole mass analyzer and positive mode electrospray ionization, using a previously optimized quick, easy, cheap, effective, rugged, and safe method for sample preparation. Validation studies, according to document SANTE/11945/2015, demonstrated that the developed method is selective, accurate, and precise, providing recoveries of 70–120%, relative standard deviations ≤20% and quantification limits from 3 μg/kg. The method was compared with one based on high-performance liquid chromatography with tandem mass spectrometry, in terms of chromatographic performance, detectability and matrix effect for five varieties of lettuce. The new method provided a reduction in the time for the chromatographic analysis of 50%, from 30 to 15 min, using a lower mobile phase flow rate (0.147 mL/min), which reduced the consumption of mobile phase by 25%, and injection of smaller amounts of sample (1.7 μL). Lower limits of quantification were obtained for almost all pesticides studied for green-leaf lettuce. However, in relation to the matrix effect, four of the five types of lettuce studied presented higher matrix effects.



Synthesis of polydopamine-functionalized magnetic graphene and carbon nanotubes hybrid nanocomposites as an adsorbent for the fast determination of 16 priority polycyclic aromatic hydrocarbons in aqueous samples

2018-02-06T12:45:33.68393-05:00

A novel adsorbent made of polydopamine-functionalized magnetic graphene and carbon nanotubes hybrid nanocomposite was synthesized and applied to determine 16 priority polycyclic aromatic hydrocarbons by magnetic solid phase extraction in water samples. FTIR spectroscopy, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy consistently indicate that the synthesized adsorbents are made of core–shell nanoparticles well dispersed on the surface of graphene and carbon nanotubes. The major factors affecting the extraction efficiency, including the pH value of samples, the amount of adsorbent, adsorption time and desorption time, type and volume of desorption solvent, were systematically optimized. Under the optimum extraction conditions, a linear response was obtained for polycyclic aromatic hydrocarbons between concentrations of 10 and 500 ng/L with the correlation coefficients ranging from 0.9958 to 0.9989, and the limits of detection (S/N = 3) were between 0.1 and 3.0 ng/L. Satisfactory results were also obtained when applying these magnetic graphene/carbon nanotubes/polydopamine hybrid nanocomposites to detect polycyclic aromatic hydrocarbons in several environmental aqueous samples.



Analysis of trace levels of impurities and hydrogen isotopes in helium purge gas using gas chromatography for tritium extraction system of an Indian lead lithium ceramic breeder test blanket module

2018-02-06T12:45:00.162208-05:00

In the fusion fuel cycle, the accurate analysis and understanding of the chemical composition of any gas mixture is of great importance for the efficient design of a tritium extraction and purification system or any tritium handling system. Methods like laser Raman spectroscopy and gas chromatography with thermal conductivity detector have been considered for hydrogen isotopes analyses in fuel cycles. Gas chromatography with a cryogenic separation column has been used for the analysis of hydrogen isotopes gas mixtures in general due to its high reliability and ease of operation. Hydrogen isotopes gas mixture analysis with cryogenic columns has been reported earlier using different column materials for percentage level composition. In the present work, trace levels of hydrogen isotopes (∼100 ppm of H2 and D2) have been analyzed with a Zeolite 5A and a modified γ-Al2O3 column. Impurities in He gas (∼10 ppm of H2, O2, and N2) have been analyzed using a Zeolite 13-X column. Gas chromatography with discharge ionization detection has been utilized for this purpose. The results of these experiments suggest that the columns developed were able to separate ppm levels of the desired components with a small response time (<6 min) and good resolution in both cases.



Rapid characterization of chlorogenic acids in Duhaldea nervosa based on ultra-high-performance liquid chromatography–linear trap quadropole-Orbitrap-mass spectrometry and mass spectral trees similarity filter technique

2018-02-06T12:44:48.118931-05:00

Duhaldea nervosa (Wallich ex Candolle) A. Anderberg has been traditionally used as a food spice and also in folk medicine for treating traumatic injury and relieving rheumatism, especially accelerating the healing of a fracture. However, so far as we are aware, the chemical constituents have not been fully investigated. In this study, a practical method of mass spectral trees similarity filter, a data-mining technique, was developed and evaluated for the rapid detection and identification complicated constituents based on ultra-high-performance liquid chromatography–linear trap quadropole-Orbitrap-mass spectrometry. Finally, a total of 47 chlorogenic acids, including 19 monoacyl-quinic acids, 22 diacyl-quinic acids, and six triacyl-quinic acids, were unambiguously or tentatively identified based on their accurate mass measurement, chromatographic retention, MSn spectra, and bibliography data. To our best knowledge, it is the first time to report the chlorogenic acids of D. nervosa, which would be beneficial for the further material basis and quality research. Meanwhile, this mass spectral trees similarity filter method could be envisioned to exhibit a wide application for the identification of complicated components from botanical extracts.



Ionic liquid chemically bonded basalt fibers for in-tube solid-phase microextraction

2018-02-06T12:44:36.968142-05:00

Ionic liquids have been widely used in different fields by advantage of their specific properties. In this work, 1-methyl-3-(3-trimethoxysilyl propyl)imidazolium chloride was prepared and chemically bonded onto basalt fibers for in-tube solid-phase microextraction. Through combining in-tube extraction device with high-performance liquid chromatography equipped with a diode array detector, an online enrichment and analysis method for eight polycyclic aromatic hydrocarbons was established under the optimum conditions. A good enrichment factor (52–814), good linearity (0.10–15 and 0.20–15 μg/L), low limits of detection (0.03–0.05 μg/L), and low limits of quantitation (0.10–0.20 μg/L) were achieved using a sample volume of 50 mL. Analysis method was applied to the real samples including the groundwater and wastewater from a chemical industry park, some target analytes were detected and the relative recoveries were in the range of 80.4–116.8%.



Determination of synephrine in feeds by a novel quick, easy, cheap, effective, rugged, and safe solid-phase extraction method combined with UHPLC–MS/MS

2018-02-06T12:44:22.748658-05:00

To detect and quantify synephrine in feed, an effective analytical method based on quick, easy, cheap, effective, rugged, and safe solid-phase extraction coupled to ultra high performance liquid chromatography with tandem mass spectrometry was developed with isotopic internal standards. Pretreatment was performed using quick, easy, cheap, effective, rugged, and safe solid-phase extraction with primary secondary amine and C18 sorbent as sorbents in combination with Oasis MCX column clean-up to extract and purify feed samples. Tandem mass spectrometry detection in positive ion mode was conducted in positive multiple reaction monitoring mode in addition to the quantitative internal standard method. Two transitions of synephrine at m/z 168.1/150.0 and 168.1/135.0 were selected, and m/z 168.1/135.0 was determined as the quantification ion pair. D9-Terbutaline was selected as an internal standard, for which m/z 235.1/153.0 was selected as the quantification ion pair. Good linearity was shown for synephrine in the range of 0.5–50 μg/L, and the correlation coefficient exceeded 0.999. The recoveries in three different feed samples at three spiked levels were 81.42–112.08%, and the relative standard deviations were not greater than 14.66%. The method proposed in this study was reliable and highly effective, and its sensitivity, accuracy, and precision are suitable for determining synephrine residues in feed samples.



Chiral ligand exchange countercurrent chromatography: Enantioseparation of amino acids

2018-02-06T12:44:09.454323-05:00

This work deals with the enantioseparation of α-amino acids by chiral ligand exchange high-speed countercurrent chromatography using N-n-dodecyl-l-hydroxyproline as a chiral ligand and copper(II) as a transition metal ion. A biphasic solvent system composed of n-hexane/n-butanol/aqueous phase with different volume ratios was selected for each α-amino acid. The enantioseparation conditions were optimized by enantioselective liquid–liquid extractions, in which the main influence factors, including type of chiral ligand, concentration of chiral ligand and transition metal ion, separation temperature, and pH of the aqueous phase, were investigated for racemic phenylalanine. Altogether, we tried to enantioseparate 15 racemic α-amino acids by the analytical countercurrent chromatography, of which only five of them could be successfully enantioseparated. Different elution sequence for phenylalanine enantiomer was observed compared with traditional liquid chromatography and the proposed interactions between chiral ligand, transition metal ion (Cu2+), and enantiomer are discussed.



Enantioselective and simultaneous determination of lactate and 3-hydroxybutyrate in human plasma and urine using a narrow-bore online two-dimensional high-performance liquid chromatography system

2018-02-05T03:50:41.562597-05:00

For the enantioselective and simultaneous analysis of lactate and 3-hydroxybutyrate, a validated online two-dimensional high-performance liquid chromatography system using 4-nitro-7-piperazino-2,1,3-benzoxadiazole as a fluorescent derivatization reagent has been developed. For the reversed-phase separation in the first dimension, a Capcell Pak C18 ACR column (1.5 × 250 mm, particle size 3 μm) was used, and the target fractions were isolated by their hydrophobicity. In the second dimension, a polysaccharide-coated enantioselective column, Chiralpak AD-H (2.0 × 250 mm, 5 μm), was used. The system was validated by the calibration curve, intraday precision, interday precision, and accuracy using standards and real human samples, and satisfactory results were obtained. The present method was applied to human plasma and urine, and in the plasma, trace amounts of d-lactate (8.4 μM) and l-3-hydroxybutyrate (1.0 μM), besides high levels of l-lactate (860.9 μM) and d-3-hydroxybutyrate (59.4 μM), were successfully determined. In urine, trace levels of d-lactate (3.7 μM), d-3-hydroxybutyrate (2.3 μM), and l-3-hydroxybutyrate (3.3 μM) in addition to a relatively large amount of l-lactate (15.4 μM) were observed. The present online two-dimensional high-performance liquid chromatography system is useful for the simultaneous determination of all the lactate and 3-hydroxybutyrate enantiomers in human physiological fluids, and further clinical applications are ongoing.



Enantioselective ultra high performance liquid and supercritical fluid chromatography: The race to the shortest chromatogram

2018-02-02T03:06:22.930375-05:00

The ever-increasing need for enantiomerically pure chiral compounds has greatly expanded the number of enantioselective separation methods available for the precise and accurate measurements of the enantiomeric purity. The introduction of chiral stationary phases for liquid chromatography in the last decades has revolutionized the routine methods to determine enantiomeric purity of chiral drugs, agrochemicals, fragrances, and in general of organic and organometallic compounds. In recent years, additional efforts have been placed on faster, enantioselective analytical methods capable to fulfill the high throughput requirements of modern screening procedures. Efforts in this field, capitalizing on improved chromatographic particle technology and dedicated instrumentation, have led to highly efficient separations that are routinely completed on the seconds time scale. An overview of the recent achievements in the field of ultra-high-resolution chromatography on column packed with chiral stationary phases, both based on sub-2 μm fully porous and sub-3 μm superficially porous particles, will be given, with an emphasis on very recent studies on ultrafast chiral separations.



Application of micro-solid-phase extraction for the on-site extraction of heterocyclic aromatic amines in seawater

2018-02-01T05:37:06.406086-05:00

An efficient on-site extraction technique to determine carcinogenic heterocyclic aromatic amines in seawater has been reported. A micro-solid-phase extraction device placed inside a portable battery-operated pump was used for the on-site extraction of seawater samples. Before on-site applications, parameters that influence the extraction efficiency (extraction time, type of sorbent materials, suitable desorption solvent, desorption time, and sample volume) were investigated and optimized in the laboratory. The developed method was then used for the on-site sampling of heterocyclic aromatic amines determination in seawater samples close to distillation plant. Once the on-site extraction completed, the small extraction device with the analytes was brought back to the laboratory for analysis using high-performance liquid chromatography with fluorescence detection. Based on the optimized conditions, the calibration curves were linear over the concentration range of 0.05–20 μg/L with correlation coefficients up to 0.996. The limits of detection were 0.004–0.026 μg/L, and the reproducibility values were between 1.3 and 7.5%. To evaluate the extraction efficiency, a comparison was made with conventional solid-phase extraction and it was applied to various fortified real seawater samples. The average relative recoveries obtained from the spiked seawater samples varied in the range 79.9–95.2%.



Comparison between core–shell and totally porous particle stationary phases for fast and green LC determination of five hepatitis-C antiviral drugs

2018-02-01T05:36:53.2174-05:00

The performances of core–shell 2.7 μm and fully porous sub-2 μm particles packed in narrow diameter columns were compared under the same chromatographic conditions. The stationary phases were compared for fast separation and determination of five new antiviral drugs; daclatasvir, sofosbuvir, velpatasvir, simeprevir, and ledipasvir. The gradient elution was done using ethanol as green organic modifier, which is more environmentally friendly. Although both columns provided very good resolution of the five drugs, core–shell particles had proven to be of better efficiency. Under gradient elution conditions, core–shell particles exhibited faster elution, better peak shape, and enhanced resolution adding to lower system backpressure. The column backpressure on sub-2 μm particles was more than twice that on core–shell particles. This gives a chance to use conventional high-performance liquid chromatography conditions without needing special instrumentation as that required for ultra-high performance liquid chromatography. The method was validated for determination of the five drugs by gradient elution using mobile phase composed of organic modifier ethanol and aqueous part containing 0.75 g sodium octane sufonate and 3.0 g sodium dihydrogen phosphate per liter at pH of 6.15. Detection was done using UV-detector set at 210 nm. The linearity, accuracy, and precision were found very good within the concentration range of 2–200 μg/mL.



A combination of dispersive liquid–liquid microextraction and surface plasmon resonance sensing of gold nanoparticles for the determination of ziram pesticide

2018-02-01T04:36:28.620956-05:00

We have developed a reliable, fast, and highly sensitive analytical method utilizing dispersive liquid–liquid microextraction and gold nanoparticles probes for ziram (zinc bis(dimethyldithiocarbamate)) determination. The method is based on the in situ formation of gold nanoparticles in carbon tetrachloride as an organic phase. It was found that the trace levels of ziram influenced the formation of gold nanoparticles, leading to absorbance change of a sedimented phase. The results of the colorimetric ziram determination were in the concentration range of 0.12–2.52 ng/mL with a limit of detection of 0.06 ng/mL. The formation of the stable and dispersed gold nanoparticles in the organic phase provides a good precision for dispersive liquid–liquid microextraction method, resulting in the relative standard deviation of 3.8 and 1.2% for 0.56 and 1.58 ng/mL of ziram, respectively. This method has been successfully used for the ziram determination in samples of well and river water, soil, potato, carrot, wheat, and paddy soil.



Optimization of the surface modification process of cross-linked polythiol-coated chiral stationary phases synthesized by a two-step thiol-ene click reaction#

2018-02-01T04:36:17.394679-05:00

A new platform technology for the preparation of stable chiral stationary phases was successfully optimized. The chiral selector tert-butylcarbamoylquinine was firstly covalently connected to the polymer poly(3-mercaptopropyl)methylsiloxane by thiol-ene click reaction. Secondly, the quinine carbamate functionalized polysiloxane conjugate was coated onto the surface of vinyl modified silica particles and cross-linked via thiol-ene click reaction. The amount of polysiloxane, chiral selector, radical initiator, reaction solvent (chloroform and methanol), reaction time, and pore size of the supporting silica particles were varied and systematically optimized in terms of achievable plate numbers while maintaining simultaneously enantioselectivity. The optimization was based on elemental analysis data, chromatographic results, and H/u-curves (Van Deemter) of the resultant chiral stationary phases. The results suggest that better chromatographic efficiency (higher plate numbers) at equal enantioselectivity can be achieved with methanol (a poor solvent for the polysiloxane that is dispersed rather than dissolved) and a lower film thickness of quinine carbamate functionalized polysiloxane. In this study, chiral stationary phases based on 100 Å silica slightly outperformed 200 Å silica particles (each 5 μm). The optimized two step material exhibited significantly reduced mass transfer resistance compared to the one step material and equal performance as a brush-type chiral stationary phase.



HPLC–MS/MS determination of flavonoids in Gleditsiae Spina for its quality assessment

2018-02-01T04:36:07.093304-05:00

Gleditsiae Spina, the thorn of Gleditsia sinensis Lam., has been used as an anti-inflammatory, anti-tumor, and anti-bacterial traditional medicine for hundreds of years in China. This study used high-performance liquid chromatography and tandem mass spectrometry combined with chemometric methods to allow the fast and accurate identification and quantification of the flavonoids compounds in Gleditsiae Spina, and created reliable criteria for accurate identification of Gleditsiae Spina and its adulterants. This research provides good evidence for the classification and quality evaluation of Gleditsiae Spina. Firstly, eight flavonoids compounds were detected and identified on the basis of their mass spectra, fragment characteristics, and comparison with published data. Then the mass spectroscopic fragmentation pathways of these compounds were determined and, in addition rutin, isoquercitrin, and quercitrin were detected in Gleditsiae Spina for the first time. The quantification was performed on a triple quadrupole tandem mass spectrometer in multi-reaction monitoring mode, and the baseline separation of the eight bioactive flavonoids components was achieved within 13 min. Furthermore, the proposed method was successfully applied for simultaneous quantitative determination of the eight Gleditsiae Spina compounds and adulterants obtained from different sources in China. Then, we built a classification model which showed a high level of accuracy predicting 100% of the samples, correctly.



A convenient ultrasound-assisted saponification for the simultaneous determination of vitamin E isomers in vegetable oil by HPLC with fluorescence detection

2018-02-01T04:35:45.258901-05:00

An efficient ultrasound-assisted saponification was developed for simultaneous determination of vitamin E isomers in vegetable oil by high-performance liquid chromatography with fluorescence detection. The samples were saponified ultrasonically with potassium hydroxide solution for only 7 min, then the analytes were extracted with ether. Vitamin E isomers were separated on a C18 column at 25°C with a mobile phase of methanol/acetonitrile (81:19, v/v) at a flow rate of 0.8 mL/min. Fluorescence detection was operated at 290 nm of excitation wavelength and 327 nm of emission wavelength. Under the optimized conditions, good linearities over the range of 0.001–8.00 μg/mL (r > 0.999) were obtained. Mean recoveries of the method were 88.0–106%, with intra- and interday RSDs less than 11.8 and 12.8%, respectively. The detection limits and quantification limits of the method were 0.30–1.8 and 1.0–6.1 μg/kg, respectively. The recoveries of this method were much higher than that of the quick, easy, cheap, effective, rugged, and safe method and direct dilution method, but were similar to those of hot saponification. This proposed method provides reliable, simple, and rapid quantification of vitamin E isomers in vegetable oils. Five kinds of vegetable oils were analyzed, the quantification results were within the ranges reported by other authors.



Flotation/ultrasound-assisted microextraction followed by HPLC for determination of fat-soluble vitamins in multivitamin pharmaceutical preparations

2018-02-01T04:30:32.589653-05:00

Dissolved carbon dioxide flotation–emulsification microextraction technique coupled with high-performance liquid chromatography was developed for separation and determination of fat-soluble vitamins (A, D3, E, and K3) in multivitamin pharmaceutical preparations. Dissolved carbon dioxide flotation was used to break up the emulsion of extraction solvent in water and to collect the extraction solvent on the surface of aqueous sample in narrowed capillary part of extraction cell. Carbon dioxide bubbles were generated in situ through the addition of 300 μL of concentrated hydrochloric acid into the alkaline sample solution at pH = 11.5 (1% w/v sodium carbonate), which was sonicated to intensify the carbon dioxide bubble generation. Several factors affecting the extraction process were optimized. Under the optimal conditions, the limits of detection were 0.11, 0.47, 0.20 and 0.35 μg/L for A, E, D3, and K3 vitamins in water samples, respectively. The inter-day and intra-day precision of the proposed method were evaluated in terms of the relative standard deviation and were <10.5%.



Van't Hoff analysis in chiral chromatography

2018-01-31T12:32:54.056648-05:00

The present review discusses the theory and application of van't Hoff analysis in chiral chromatography, with main focus on liquid chromatography. The topics considered include the physical meaning of van't Hoff equation's parameters, interpretation of thermodynamic data in terms of retention and enantioseparation mechanisms, abnormal behavior of van't Hoff plots, and best practices to avoid biased results.



Systematic study on metabolism and activity evaluation of Radix Scutellaria extract in rat plasma using UHPLC with quadrupole time-of-flight mass spectrometry and microdialysis intensity-fading mass spectrometry

2018-01-31T12:31:55.628973-05:00

Radix Scutellaria is a widely used traditional Chinese medicine in the treatment of various diseases. However, the activities of the absorbed components and metabolites of its main flavones in rat plasma need further investigation. In this study, a systematic method based on ultra-high performance liquid chromatography with quadruple time-of-flight mass spectrometry was developed to speculate the absorbed components and metabolites of the main flavonoids in Radix Scutellaria extract in rat plasma sample after oral administration of the extract. Twelve compounds, including four prototype components and eight metabolites, were confirmed in drug-containing plasma. In these metabolites, five were originally detected in rat plasma. The possible metabolic pathways of these polyhydroxy flavones in vivo were described and clarified. Microdialysis with intensity-fading mass spectrometry was originally employed to investigate the binding affinities of the absorbed components and metabolites with α-glucosidase. The order of their binding affinities was P4 > P3 > P2 > P1≥M5 > M3 > M1. The research result is helpful to deepen the understanding of the absorbed components and metabolic pathways of main flavones from Radix Scutellaria, and provide a new approach to screen potential inhibitors from in vivo components originated from Chinese herb.



β-Cyclodextrin polymer@Fe3O4 based magnetic solid-phase extraction coupled with HPLC for the determination of benzoylurea insecticides from honey, tomato, and environmental water samples

2018-01-31T12:02:47.335792-05:00

In this work, a magnetic β-cyclodextrin polymer was successfully prepared and used as an adsorbent for the magnetic solid-phase extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, flufenoxuron, and chlorfluazuron) from honey, tomato, and environmental water samples. The influence of the main experimental conditions on the extraction was studied. Under the optimized conditions, the β-cyclodextrin polymer@Fe3O4 showed an excellent extraction performance for the benzoylurea insecticides. A good linearity was obtained for the analytes in the range of 3.0–800 ng/g for honey samples, 0.3–160 ng/g for tomato samples, and 0.1–80.0 ng/mL for water samples, with the correlation coefficients above 0.9998. Satisfactory repeatabilities were achieved, with the relative standard deviations less than 5.7%. The limits of detection (S/N = 3) of the method for the benzoylurea insecticides were 0.2–0.8 ng/g for honey samples, 0.04–0.10 ng/g for tomato samples, and 0.02–0.05 ng /mL for water samples. The method was successfully used for the determination of the six benzoylurea insecticides residues in honey, tomato, and environmental water samples with a satisfactory result.



Dispersive magnetic solid-phase extraction of phthalate esters from water samples and human plasma based on a nanosorbent composed of MIL-101(Cr) metal–organic framework and magnetite nanoparticles before their determination by GC–MS

2018-01-30T07:56:22.21717-05:00

In this study, a magnetic metal–organic framework was synthesized simply and utilized in the dispersive magnetic solid-phase extraction of five phthalate esters followed by their determination by gas chromatography with mass spectrometry. First, MIL-101(Cr) was prepared hydrothermally in water medium without using highly corrosive hydrofluoric acid, utilizing an autoclave oven heat supply. Afterward, Fe3O4 nanoparticles were decorated into the matrix of MIL-101(Cr) to fabricate magnetic MIL-101 nanocomposite. The nanocomposite was characterized by various techniques. The parameters affecting dispersive magnetic solid-phase extraction efficiency were optimized and obtained as: a sorbent amount of 15 mg; a sorption time of 20 min; an elution time of 5 min; NaCl concentration, 10% w/v; type and volume of the eluent 1 mL n-hexane/acetone (1:1 v/v). Under the optimum conditions detection limits and linear dynamic ranges were achieved in the range of 0.08–0.15 and 0.5–200 μg/L, respectively. The intra- and interday RSD% values were obtained in the range of 2.5–9.5 and 4.6–10.4, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of the model analytes in water samples, and human plasma in the range of microgram per liter and satisfactory results were obtained.



Sol–gel niobia sorbent with a positively charged octadecyl ligand providing enhanced enrichment of nucleotides and organophosphorus pesticides in capillary microextraction for online HPLC analysis

2018-01-30T07:55:33.512842-05:00

A niobia-based sol–gel organic–inorganic hybrid sorbent carrying a positively charged C18 ligand (Nb2O5-C18(+ve)) was synthesized to achieve enhanced enrichment capability in capillary microextraction of organophosphorus compounds (which include organophosphorus pesticides and nucleotides) before their online analysis by high-performance liquid chromatography. The sorbent was designed to simultaneously provide three different types of molecular level interactions: electrostatic, Lewis acid–base, and van der Waals interactions. To understand relative contributions of various molecular level analyte–sorbent interactions in the extraction process, two other sol–gel niobia sorbents were also created: (a) a purely inorganic sol–gel niobia sorbent (Nb2O5) and (b) an organic–inorganic hybrid sol–gel niobia sorbent carrying an electrically neutral-bonded octadecyl ligand (Nb2O5-C18). The extraction efficiency of the created sol–gel niobia sorbent (Nb2O5-C18 (+ve)) was compared with that of analogously designed and synthesized titania-based sol–gel sorbent (TiO2-C18 (+ve)), taking into consideration that titania-based sorbents present state-of-the-art extraction media for organophosphorus compounds. In capillary microextraction with high-performance liquid chromatography analysis, Nb2O5-C18 (+ve) had shown 40–50% higher specific extraction values (a measure of extraction efficiency) over that of TiO2-C18 (+ve). Compared to TiO2-C18(+ve), Nb2O5-C18(+ve) also provided superior analyte desorption efficiency (96 vs. 90%) during the online release of the extracted organophosphorus pesticides from the sorbent coating in the capillary microextraction capillary to the chromatographic column using reversed-phase high-performance liquid c[...]



Characterization and application of a lanthanide-based metal–organic framework in the development and validation of a matrix solid-phase dispersion procedure for pesticide extraction on peppers (Capsicum annuum L.) with gas chromatography–mass spectrometry

2018-01-26T12:16:07.821131-05:00

The metal–organic framework [(La0.9Sm0.1)2(DPA)3(H2O)3]∞ was synthetized and characterized by X-ray diffractometry, differential thermogravimetric analysis, and infrared spectroscopy. The material was tested for the development and validation of a matrix solid-phase dispersion procedure for extraction of atrazine, bifenthrin, bromuconazole, clofentezine, fenbuconazole, flumetralin, procymidone, and pirimicarb, from peppers, with analysis using gas chromatography with mass spectrometry in the selected ion monitoring mode. The method developed was linear over the range tested (50.0–1000.0 μg/kg for procymidone and 200.0–1000.0 μg/kg for all other pesticides), with correlation coefficients ranging from 0.9930 to 0.9992. Experiments were carried out at 250.0, 500.0, and 1000.0 μg/kg fortification levels, and resulted in recoveries in the range of 52.7–135.0%, with coefficient of variation values between 5.2 and 5.4%, respectively, for [(La0.9Sm0.1)2(DPA)3(H2O)3]∞ sorbent. Detection and quantification limits ranged from 16.0 to 67.0 μg/kg and from 50.0 to 200.0 μg/kg, respectively, for the different pesticides studied. The results were compared with literature data. The developed and validated method was applied to real samples. The analysis detected the presence of residues of pesticides procymidone, fenbuconazole, flumetralin, clofentezine, atrazine, and bifenthrin.



Comparison of commercial organic polymer-based and silica-based monolithic columns using mixtures of analytes differing in size and chemistry

2018-01-26T12:16:03.324449-05:00

Commercially available silica-based monolithic columns Chromolith RP-8e, Chromolith RP-18, and Chromolith HR RP-18, and polymer-based monolithic columns ProSwift RP-1S, ProSwift RP-2H, and ProSwift RP-3U varying in pore size and bonded phase have been tested for the fast separation of selected sets of analytes. These mixtures of analytes included small molecules (uracil, caffeine, 1-phenylethanol, butyl paraben, and anthracene), acylated insulins, and intact proteins (ribonuclease A, cytochrome C, transferrin, apomyoglobin, and thyroglobulin), and covered wide range of chemistries and sizes. Small molecules were well separated with a height equivalent to theoretical plate of 11–26 μm using silica-based monolithic columns, while organic polymer-based monoliths excelled in the fast sub 1 min baseline separations of large molecules. A peak capacity of 37 was found for separation of acylated insulins on Chromolith columns using a 3 min gradient at a flow rate of 3 ml/min. Poor recovery of proteins from Chromolith columns and significant peak tailing of small molecules using ProSwift columns were the major obstacles in using monolithic columns in those applications.



Dispersion-assisted quick and simultaneous extraction of 30 pesticides from alcoholic and non-alcoholic drinks with the aid of experimental design

2018-01-26T12:15:53.232267-05:00

The presence of pesticides in food items and beverages is a big threat to humankind, and their quantitative estimation with high precision and accuracy is always a challenge for analytical chemists. Hence, a simple and rapid method is proposed for the simultaneous determination of 30 pesticides in beverages (alcoholic and non-alcoholic drinks). The proposed method hyphenated with triple quadrupole liquid chromatography mass spectrometry has only 2 min chromatographic runtime for the analysis of all the pesticides. All the factors affecting the extraction yield have been optimized using an experimental design; and under optimized conditions, the developed method has been validated. The detection limits for all the pesticides were in the range of 0.001–0.348 μg/L with good linearity in the concentration range of 0.01–80.0 μg/L. The coefficient of determination was in the range of (R2) ≥ 0.977 to 0.999 for all the pesticides. The method was also checked for the precision of the relative standard deviation, which was below 4.75 (intra-day) and 8.96% (inter-day). The recovery of the method was 92–138%.



Determination and dissipation of afidopyropen and its metabolite in wheat and soil using QuEChERS–UHPLC–MS/MS

2018-01-26T12:15:30.319215-05:00

The dissipations of afidopyropen and its metabolite in wheat plant and soil were determined using a quick, easy, cheap, effective, rugged, and safe method with ultra-high performance liquid chromatography and tandem mass spectrometry under a field ecosystem. The limits of quantification were estimated for both target compounds as 0.001 mg/kg. The recoveries of afidopyropen and its metabolite ranged from 94 to 114% (soil), 90 to 109% (wheat seed) and 81 to 91% (wheat straw) at levels of 0.001, 0.01, 0.1, and 2.0 mg/kg with relative standard deviations ≤7%. The results of the residual dynamics experiments showed that afidopyropen dissipated rapidly in wheat plant and soil. Its metabolite initially showed a tendency of rapid increase followed by a decrease in wheat plant but could not be detected in soil. The data showed that the first + first-order model was more suitable for describing the decline of afidopyropen in wheat and soil. The half-lives of afidopyropen in wheat plant and soil were 1.65 and 1.21 days, respectively.



Rapid characterization of the absorbed chemical constituents of Tangzhiqing formula following oral administration using UHPLC–Q-TOF-MS

2018-01-26T09:03:47.599546-05:00

Tangzhiqing formula, a Chinese herbal formula, is used for the treatment of type II diabetes and prediabetes. Although its effectiveness has been certified by clinical use, its absorbed chemical constituents are not comprehensively represented. Thence, in order to reveal potential bioactive components and metabolism of Tangzhiqing formula, an ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry method was developed. A total of 86 absorbed components, including 38 prototype compounds and 48 metabolites, were identified in rat plasma, urine, and feces after oral administration of Tangzhiqing formula. This was the first systematic study on the chemical constituents and metabolic profiling of Tangzhiqing formula. The results indicated that alkaloids and flavonoids were main absorbed components, and glucuronidation and sulfation were the major metabolites. Moreover we concluded that alkaloids and flavonoids first underwent demethylation and hydrolysis reactions before biotransformed to phase II metabolites. This study provided valuable data for safety estimation of Tangzhiqing formula, which will be advantageous for clinical application.



In situ derivatization and hollow-fiber liquid-phase microextraction to determine sulfonamides in water using UHPLC with fluorescence detection

2018-01-26T05:50:54.952447-05:00

A sensitive method for determining sulfonamides in water was developed and validated through in situ derivatization and hollow-fiber liquid-phase microextraction with ultra-high performance liquid chromatography and fluorescence detection. The target sulfonamides were sulfadiazine, sulfacetamide, sulfamerazine, sulfamethazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfamethoxazole, and sulfisoxazole. Following in situ derivatization with fluorescamine, three-phase hollow-fiber liquid-phase microextraction with an S 6/2 polypropylene hollow-fiber membrane was applied automatically using a multipurpose autosampler. Experimental parameters including derivatization time, choice of organic phase, pH of donor and acceptor phase, stirring rate, extraction temperature and time were optimized. Under optimized conditions, the target sulfonamides achieved excellent linearity with correlation coefficients of 0.9924–0.9994 within the concentration range of 0.05–5 μg/L. The limits of detection of the eight sulfonamides were 3.1–11.2 ng/L, and the limits of quantification were 10.3–37.3 ng/L. Enrichment factors of 0.1 and 5 μg/L sulfonamides spiked in lake water were 14–60, and recoveries were 56–113% with relative standard derivations of 3–19%. Applied with the developed method, sulfamerazine and sulfamethoxazole were measurable in both influent and effluent water of the three sewage treatment plants in Guangzhou, China. The developed method was sensitive and provided an alternative method for simultaneously enriching and quantifying multiple sulfonamides in environmental water.



Magnetic iron(III)-based framework composites for the magnetic solid-phase extraction of fungicides from environmental water samples

2018-01-26T04:40:43.927723-05:00

We adopted a facile hydrofluoric acid-free hydro-/solvothermal method for the preparation of four magnetic iron(III)-based framework composites (MIL-101@Fe3O4-COOH, MIL-101-NH2@Fe3O4-COOH, MIL-53@Fe3O4-COOH, and MIL-53-NH2@Fe3O4-COOH). The obtained four magnetic iron(III)-based framework composites were applied to magnetic separation and enrichment of the fungicides (prochloraz, myclobutanil, tebuconazole, and iprodione) from environmental samples before high-performance liquid chromatographic analysis. MIL-101-NH2@Fe3O4-COOH showed more remarkable pre-concentration ability for the fungicides as compared to the other three magnetic iron(III)-based framework composites. The extraction parameters affecting enrichment efficiency including extraction time, sample pH, elution time, and the desorption solvent were investigated and optimized. Under the optimized conditions, the standard curve of correlation coefficients were all above 0.991, the limits of detection were 0.04–0.4 μg/L, and the relative standard deviations were below 10.2%. The recoveries of two real water samples ranged from 71.1–99.1% at the low spiking level (30 μg/L). Therefore, the MIL-101-NH2@Fe3O4-COOH composites are attractive for the rapid and efficient extraction of fungicides from environmental water samples.



Cellulose tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase for the enantioseparation of drugs in supercritical fluid chromatography: comparison with HPLC

2018-01-26T04:40:29.961288-05:00

A cellulose tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase was studied as a tool for the enantioselective separation of 21 selected analytes with different pharmaceutical and physicochemical properties. The enantioseparations were performed using supercritical fluid chromatography. The effect of the mobile phase composition was studied. Four different additives (diethylamine, triethylamine, isopropylamine, and trifluoroacetic acid) and isopropylamine combined with trifluoroacetic acid were tested and their influence on enantioseparation was compared. The influence of two different mobile phase co-solvents (methanol and propan-2-ol) combined with all the additives was also evaluated. The best mobile phase compositions for the separation of the majority of enantiomers were CO2/methanol/isopropylamine 80:20:0.1 v/v/v or CO2/propan-2-ol/isopropylamine/trifluoroacetic acid 80:20:0.05:0.05 v/v/v/v. The best results were obtained from the group of basic β-blockers. A high-performance liquid chromatography separation system composed of the same stationary phase and mobile phase of similar properties prepared as a mixture of hexane/propan-2-ol/additive 80:20:0.1 v/v/v was considered for comparison. Supercritical fluid chromatography was found to yield better results, i.e. better enantioresolution for shorter analysis times than high-performance liquid chromatography. However, examples of enantiomers better resolved under the optimized conditions in high-performance liquid chromatography were also found.



Determination of 3-chloro-1,2-propanediol in polyamideamine epichlorohydrin resin solution by reaction-based headspace gas chromatography

2018-01-26T04:30:24.025067-05:00

We report on a headspace gas chromatographic method for determining the content of 3-chloro-1,2-propanediol in polyamideamine epichlorohydrin resin solution. It was based on quantitatively converting 3-chloro-1,2-propanediol to formaldehyde by periodate oxidation in a closed headspace sample vial at a room temperature for 10 min, and then to methanol by borohydride reduction at 90°C for 40 min followed by the headspace gas chromatographic measurement. The results showed that the present method has an excellent measurement precision (relative standard deviation < 2.60%) and accuracy (recoveries from 96.4–102%) in 3-chloro-1,2-propanediol analysis. The limit of quantitation was 0.031 mg/mL. It is simple and suitable for determining the 3-chloro-1,2-propanediol content in polyamideamine epichlorohydrin resin solution.



Efficient preparative separation of β-cypermethrin stereoisomers by supercritical fluid chromatography with a two-step combined strategy

2018-01-25T09:43:57.85743-05:00

An efficient two-step method has been developed for the separation of β-cypermethrin stereoisomers by supercritical fluid chromatography with polysaccharide chiral stationary phases. With respect to retention, selectivity, and resolution of β-cypermethrin, the effects of chiral stationary phases, cosolvents, mobile phases, and column temperature have been studied in detail. Through a two-step separation, β-cypermethrin was firstly separated by using a cellulose-derived chiral stationary phase to obtain two stereoisomeric pairs, and further resolved on an amylose-based chiral stationary phase to produce four enantiopure stereoisomers. The electronic circular dichroism patterns of the first- and the third-eluted isomers in methanol solution showed the mirror image of each other in the wavelength range 200∼300 nm, indicating that they were a pair of enantiomers. Moreover, the second- and the fourth-eluted isomers were also enantiomers. This proposed two-step strategy showed low solvent consumption, fast separation speed, and high-purity, which may provide an effective approach for preparative separation of compounds with multiple chiral centers and difficult-to-separate multicomponent samples.



Hypercrosslinked particles for the extraction of sweeteners using dispersive solid-phase extraction from environmental samples

2018-01-25T09:43:35.977748-05:00

This work presents a new extraction material, namely, Q-100, based on hypercrosslinked magnetic particles, which was tested in dispersive solid-phase extraction for a group of sweeteners from environmental samples. The hypercrosslinked Q-100 magnetic particles had the advantage of suitable pore size distribution and high surface area, and showed good retention behavior toward sweeteners. Different dispersive solid-phase extraction parameters such as amount of magnetic particles or extraction time were optimized. Under optimum conditions, Q-100 showed suitable apparent recovery, ranging in the case of river water sample from 21 to 88% for all the sweeteners, except for alitame (12%). The validated method based on dispersive solid-phase extraction using Q-100 followed by liquid chromatography with tandem mass spectrometry provided good linearity and limits of quantification between 0.01 and 0.1 μg/L. The method was applied to analyze samples from river water and effluent wastewater, and four sweeteners (acesulfame, saccharin, cyclamate, and sucralose) were found in both types of sample.



Simultaneous enantioselective determination of six pesticides in aqueous environmental samples by chiral liquid chromatography with tandem mass spectrometry

2018-01-25T09:35:49.216115-05:00

A robust and sensitive method was developed for the enantiomeric analysis of six chiral pesticides (including metalaxyl, epoxiconazole, myclobutanil, hexaconazole, napropamide, and isocarbophos) in aquatic environmental samples. The optimized chromatographic conditions for the quantification of all the 12 enantiomers were performed with Chiralcel OD-RH column using mobile phase consisting of 0.1% aqueous formic acid and acetonitrile operated under reversed-phase conditions and then analyzed using liquid chromatography with tandem mass spectrometry. Twelve enantiomers were detected in multiple reaction monitoring mode. Solid-phase extraction and dispersive liquid–liquid microextraction were employed in this study. Response surface methodology was applied to assist in the dispersive liquid–liquid microextraction optimization. Under the optimum conditions, recoveries of pesticides enantiomers varied from 83.0 to 103.2% at two spiked levels with relative standard deviation less than 11.5%. The concentration factors were up to 1000 times. Method detection and quantification limits varied from 0.11 to 0.48 ng/L and from 0.46 to 1.49 ng/L, respectively. Finally, this method was used to determination of the enantiomers composition of the six pesticides in environmental aqueous matrices, which will help better understand the behavior of individual enantiomer and make accurate risk assessment to ecosystems.



A homochiral porous organic cage with large cavity and pore windows for the efficient gas chromatography separation of enantiomers and positional isomers

2018-01-25T08:25:51.714429-05:00

Porous organic cages composed of discrete cage molecules have attracted considerable recent attention as gas adsorption materials and separation media. In this study, we report a homochiral porous organic cage CC5 with a large cavity and pore windows as a novel stationary phase for high-resolution gas chromatographic separations. The capillary column was prepared by a static coating method. A large number of racemic compounds have been resolved on the coated capillary column, including derivatized amino acids, alcohols, alcohol amines, esters, ethers, ketones, and epoxides. It is interesting that the CC5-coated capillary column exhibits significant chiral recognition complementarity to a commercial β-DEX 120 column and a previously reported homochiral porous organic cage CC3-R-coated column, which could expand the range of the analytes amenable to separation on porous organic cage-based capillary columns. Moreover, the fabricated column also shows excellent selectivity for the separation of positional isomers, including the challenging ethylbenzene and xylene isomers. Experimental results demonstrate an excellent separation performance and stability of the CC5-coated column, making it promising for gas chromatography applications.



Air-assisted dispersive liquid–liquid microextraction based on a new hydrophobic deep eutectic solvent for the preconcentration of benzophenone-type UV filters from aqueous samples

2018-01-25T08:20:45.715111-05:00

Deep eutectic solvents are considered as new and green solvents that can be widely used in analytical chemistry such as microextraction. In the present work, a new dl-menthol-based hydrophobic deep eutectic solvent was synthesized and used as extraction solvents in an air-assisted dispersive liquid–liquid microextraction method for preconcentration and extraction of benzophenone-type UV filters from aqueous samples followed by high-performance liquid chromatography with diode array detection. In an experiment, the deep eutectic solvent formed by dl-menthol and decanoic acid was added to an aqueous solution containing the UV filters, and then the mixture was sucked up and injected five times by using a glass syringe, and a cloudy state was achieved. After extraction, the solution was centrifuged and the upper phase was subjected to high-performance liquid chromatography for analysis. Various parameters such as the type and volume of the deep eutectic solvent, number of pulling, and pushing cycles, solution pH and salt concentration were investigated and optimized. Under the optimum conditions, the developed method exhibited low limits of detection and limits of quantitation, good linearity, and precision. Finally, the proposed method was successfully applied to determine the benzophenone-type filters in environmental water samples with relative recoveries of 88.8–1[...]