Subscribe: Journal of High Resolution Chromatography
http://www3.interscience.wiley.com/rss/journal/5008460
Preview: Journal of High Resolution Chromatography

Journal of Separation Science



Wiley Online Library : Journal of Separation Science



Published: 2017-11-01T00:00:00-05:00

 



Coating of optical fiber with a smart thermosensitive polymer for the separation of phthalate esters by solid-phase microextraction

2017-11-23T03:20:32.438361-05:00

A solid-phase microextraction fiber was prepared by coating an optical fiber with a temperature-sensitive polymer to determine phthalate esters. N-Isopropylacrylamide and N,N′-methylenebisacrylamide were used as the monomer and the cross linker, respectively. The fabricated fiber was characterized by FTIR spectroscopy, thermogravimetric analysis, and scanning electron microscopy. During extraction, important factors such as extraction time, pH, temperature, and ionic strength were optimized. The fabricated fiber, which is firm, inexpensive, stable, and efficient, is a vital material used in solid-phase microextraction. Under optimum conditions, the calibration curve was linear and in the range of 1–20 μg L−1 (r2 = 0.9747). The high extraction efficiency was obtained for phthalates with a detection limit of 0.12 μg L−1. The fabricated fiber was successfully applied to the solid-phase micro extraction of phthalates from water samples after its extraction, followed by gas chromatography with flame ionization detection. This article is protected by copyright. All rights reserved



Canagliflozin stability study and eco-friendly chromatographic determination of its degradation product: A comparative study

2017-11-22T08:20:31.936234-05:00

Canagliflozin is a newly approved drug for type II diabetes mellitus. A full stability study of Canagliflozin was performed following international conference on harmonization strategies. The drug was stable against all conditions except oxidation where only one degradation product was separated and structurally elucidated using mass spectrometry and IR spectroscopy. A green high-performance thin-layer chromatographic densitometric determination was developed and validated for the accurate quantification of Canagliflozin and its main oxidative degradation product. Separation was performed on high-performance aluminum plates pre-coated with silica gel using acetone/ethanol (80:20, v/v) as a developing system and scanning at 290 nm. Retardation factor values were 0.64 and 0.81 and linearity ranges were 0.4–3.6 and 0.2–3.2 μg band−1 for the drug and the degradation product, respectively. It was a matter of interest to use green solvents with no harmful effects on the environment. The comparison between the proposed and the reported high-performance liquid chromatography method regarding greenness profile showed that the proposed method was greener and so could be used as an alternative method to the reported one with no environmental harm. Method validity was tested as per international conference on harmonization and method utility was verified by application to Invokana® tablets. This article is protected by copyright. All rights reserved



Development of a pre-column derivatization HPLC method with diode-array detection for the determination of amino sugars in peat and soil humic acids

2017-11-22T07:50:29.063025-05:00

The work is focused on the development of a high-performance liquid chromatography method with diode-array detection for the separation and quantitation of the three most abundant amino sugars; d-glucosamine, d-galactosamine, and d-mannosamine. The high-performance liquid chromatography separation was carried out by reversed-phase chromatography on Chromolith Performance RP-18e monolithic column after acid hydrolysis (5 M HCl) and pre-column derivatization of samples using diethyl ethoxymethylenemalonate. Gradient elution and a mobile phase composed of ammonium formate buffer solution (10 mmol L−1, pH 3.60) and methanol with flow rate of 1.0 mL min−1 were used. The monitoring wavelength was set at 280 nm. The limits of detection and quantitation for analytes ranged from 0.017 to 0.122 mg L−1 and from 0.057 to 0.407 mg L−1, respectively. The proposed method was successfully applied for the determination of amino sugars in samples of humic acids isolated from different soils and peat. This article is protected by copyright. All rights reserved



Exploring the enantiorecognition mechanism of Cinchona alkaloid-based zwitterionic chiral stationary phases and the basic trans-paroxetine enantiomers

2017-11-21T05:20:30.99142-05:00

The enantiomers of trans-paroxetine (the selectand) were separated on four chiral stationary phases incorporating either quinine [ZWIX(+), ZWIX(+A)] or quinidine [ZWIX(–), ZWIX(–A)] and (R,R)-aminocyclohexanesulfonic acid [in ZWIX(–), and ZWIX(+A)] or (S,S)- aminocyclohexanesulfonic acid [in ZWIX(+), and ZWIX(–A)] chiral selectors. The zwitterion nature of the phases is due to the presence of either (R,R)- or (S,S)-aminocyclohexanesulfonic acid in the selector structure bearing the quinuclidine moiety. ZWIX(+), ZWIX(–) phases are available on the market with the commercial names CHIRALPAK ZWIX(+) and CHIRALPAK ZWIX(–), respectively. With the aim of rationalizing the enantiomer elution order with the above chiral stationary phases, a molecular dynamic protocol was applied and two energetic parameters were initially measured: selectand conformational energy and selectand interaction energy. In search for other descriptors allowing a better fitting with the experimental evidences, in the present work we consider an energetic parameter, defined as the selector conformational energy, which resulted to be relevant in the explanation of the experimental elution order in most of the cases. Very importantly, the computational data produced by the present study strongly support the outstanding role of the conformational energy of the chiral selector as it interacts with the analytes. This article is protected by copyright. All rights reserved



Comparisons of glyphosate adsorption properties of different functional Cr- based metal–organic frameworks

2017-11-21T02:51:45.636939-05:00

A Cr-based metal–organic framework, namely, MIL-101(Cr), was modified with amino (NH2–) and urea (UR2–) groups, and the materials were evaluated as adsorbents for glyphosate, and a comparison with commercial activated carbon was also discussed. The effects of the adsorption factors, such as adsorbent concentration, adsorption time, pH and ionic strength were mainly investigated. The results showed that a pseudo-second-order rate equation described the adsorption kinetics mechanisms well, while the Langmuir model and the Freundlich model fitted different adsorption isotherms, respectively. Among the adsorbents we studied, NH2-MIL-101(Cr) showed the maximum adsorbing capacity, which is 64.25 mg g-1 when pH = 3.0, while UR2-MIL-101(Cr) did not reach the best adsorption performance due to the steric hindrance. The work opens up a new way for the modification of metal–organic frameworks for adsorption process. This article is protected by copyright. All rights reserved



Rapid analysis of traditional Chinese medicine Pinellia ternata by microchip electrophoresis with electrochemical detection

2017-11-20T00:50:20.458321-05:00

Traditional Chinese herbal medicine has long enjoyed the reputation of the world's most advanced system of natural medicine. Pinellia ternata is one of the most commonly used herbs in the traditional Chinese medical science. In this study five representative ingredients of Pinellia ternata guanosine, methionine, glycine, 3,4-dihydroxybenzaldehyde, and homogentisic acid, were assayed using simple derivatization procedures. Under optimized experimental condition, five analytes in Pinellia ternata were rapidly separated and detected using microchip electrophoresis, affording the benefits of speed, minimal sample requirements, and sensitive on-the-chip electrochemical detection, in 5 min with linearity over a concentration of 20–500 μM (R2 = 0.994) with nearly complete recovery (95.6–98.5%). This article is protected by copyright. All rights reserved



Screening and identification of α-glucosidase inhibitors from Shenqi Jiangtang Granule by ultrafiltration liquid chromatography and mass spectrometry

2017-11-20T00:20:32.981844-05:00

Shenqi Jiangtang Granule, a well-known traditional Chinese herbal preparation, has been widely used for the treatment of type II diabetes mellitus. In this work, an ultrafiltration liquid chromatography with quadrupole time-of-flight mass spectrometry method was proposed for the rapid identification of bioactive ingredients from Shenqi Jiangtang Granule using α-glucosidase as an example. First, the chemical profile of this preparation was clarified, including 37 saponins, 17 flavonoids, 37 lignans and 7 other compounds. After incubation with α-glucosidase in vitro, the methanol extract with an IC50 value of 0.19 mg/mL exhibited significant inhibitory activity. Then, 18 specific binding peaks were screened, and 15 peaks were identified. Among these, ten compounds were reported to have potential α-glucosidase inhibitory activity for the first time. Subsequently, the inhibitory activities of these active compounds were evaluated by ultraviolet spectrophotometry with p-nitrophenyl α-d-glucopyranoside as a substrate. As a result, gomisin J and gomisin D exhibited stronger α-glucosidase inhibitory activities than other active compounds with IC50 values of 77.69 and 133.85 μM, respectively. The results demonstrated that the integrated ultrafiltration liquid chromatography with mass spectrometry method was an effective and powerful tool for the discovery of active ingredients in Shenqi Jiangtang Granule. This article is protected by copyright. All rights reserved



Identification of proteins, drying oils, waxes and resins in the works of art micro-samples by chromatographic and mass spectrometric techniques

2017-11-18T07:20:36.409242-05:00

Simplified method for simultaneous identification of proteins, drying oils, waxes and resins in the works-of-art samples was developed. Liquid chromatography with mass spectrometry and gas chromatography with mass spectrometry were used to identify natural materials most frequently encountered in historical paintings. Protein binders were extracted with ammonia and purified using miniaturized solid-phase microextraction (Omix tips) to efficiently suppress matrix interferences. Zwitterionic stationary phase was used for separation of sixteen underivatized amino acids analysis with hydrophilic interaction liquid chromatography that were subsequently quantified with liquid chromatography with mass spectrometry. Gas chromatography with mass spectrometry was used to analyze drying oils, waxes and resins after one-step saponification/transmethylation with (m-trifluoromethylphenyl)trimethylammonium hydroxide (Meth-Prep II). While the drawback of this reagent is low reactivity towards hydroxyl groups, sample pretreatment was much simpler as compared to the other methods. Fatty acids derivatization with the Meth-Prep II reagent was compared with their silylation using N,O-bis(trimethylsilyl) trifluoroacetamide/trimethylchlorosilane mixture. It was concluded that fatty acids analysis as their methyl esters instead of trimethylsilyl esters had a minor impact on the method sensitivity. The developed method was used to analyze samples from the 16th and 17th century historical paintings. This article is protected by copyright. All rights reserved



One-pot synthesis of a multi-template molecularly imprinted polymer for the extraction of six sulfonamide residues from milk before HPLC with Diode Array Detection

2017-11-18T07:20:30.580013-05:00

A highly selective molecularly imprinted polymer sorbent was synthesized and employed for the simultaneous determination of six sulfonamide antibiotic residues (sulfanilamide, sulfacetamide, sulfadiazine, sulfathiazole, sulfamerazine and sulfamethizole) in milk samples. Multi-analyte imprinted particles were used as sorbent in solid phase extraction. Sulfonamides were separated on a high-performance liquid chromatography column (Merck-Lichrospher RP18e, 5 μm 250 × 4 mm) and further identified and quantified by diode array detection. Several parameters including required loading of the molecularly imprinted polymer sorbent, mass of milk, volume and type of elution solvent, as well as time for absorption and elution were investigated to obtain optimal experimental conditions. For comparison purpose, a non-imprinted polymer was applied under the optimum conditions. The validation study according to the European Union Decision 2002/657/EC was based on the investigation of linearity, selectivity, stability, limits of detection and quantitation, decision limit, detection capability, trueness, precision and ruggedness according to Youden's approach. The decision limit and detection capability values in the milk were achieved from 101.9 to 113.5 μg.kg−1 and from 114.4 to 135.4 μg.kg−1, respectively, depending on the target sulfonamide drug. Finally, the optimized protocol was successfully applied to commercial milk samples as well as to human breast milk. This article is protected by copyright. All rights reserved



Application of high-speed counter-current chromatography and HPLC to separate and purify of three polyacetylenes from Platycodon grandiflorum

2017-11-18T07:20:27.302139-05:00

Three polyacetylenes were isolated and purified from Platycodon grandiflorum A. DC for the first time by high-speed counter-current chromatography using a two-phase solvent system composed of hexane/ethyl acetate/methanol/water (1:31:1:31, v/v/v/v) and high-performance liquid chromatography with an Agilent ZORBAX® SB-C18 column (4.6 mm × 150 mm, 5 μm). After separation by high-speed counter-current chromatography and high-performance liquid chromatography, we obtained 3.5 mg of platetyolin A, 4.1 mg of platetyolin B, and 18.1 mg of lobetyolin with purities of 97.2, 96.7, and 96.9%, respectively. The purity of each compound was assessed by high-performance liquid chromatography and the chemical structures were evaluated by high-resolution electrospray ionization time-of-flight mass spectrometry and one- and two-dimensional NMR spectroscopy. Among the isolated compounds, platetyolin A and platetyolin B are newly reported compounds. This article is protected by copyright. All rights reserved



Rapid and green determination of 58 fragrance allergens in plush toys

2017-11-17T22:50:27.100429-05:00

This paper presents a simple, rapid, and green method based on a static headspace gas chromatography with mass spectrometry for determining 58 fragrance allergens in plush toys. This study is the first to meet the requirement for simultaneously determining 66 fragrances, except for eight natural extracts restricted by the European Toy Safety Directive 2009/48/EC. A minimal amount of sample (20 mg) and acetone solvent (20 μL) were placed in a headspace vial. A gas–solid equilibration of fragrances between the headspace and the sample was achieved within 10 min under the vapor atmosphere of acetone at 200°C, which allowed the fragrances in the sample to be measured by gas chromatography with mass spectrometry. Results showed that the interference caused by different sample matrices was negligible. The proposed method exhibited determination results that were highly similar to those of traditional ultrasonic extraction with sufficient sensitivity (limits of quantification: 0.02–10 mg/kg) for 58 fragrances, indicating its accuracy and reliability. The average recoveries ranged from 71.3 to 137.4%, and the relative standard deviation (n = 6) varied from 1.1 to 18.0%. Finally, the method was applied to monitor the fragrances in 20 commercial toys. This study provides a good reference for rapidly and greenly determining the semi-volatile analytes in toys, textiles, and other products. This article is protected by copyright. All rights reserved



Development of a high-throughput method based on thin-film microextraction using a 96-well plate system with a cork coating for the extraction of emerging contaminants in river water samples

2017-11-15T08:20:49.780537-05:00

In this study, a new method was developed in which a biosorbent material is used as the extractor phase in conjunction with a recently described sample preparation technique called thin-film microextraction and a 96-well plate system. The method was applied to the determination of emerging contaminants, such as 3-(4-methylbenzylidene) camphor, ethylparaben, triclocarban and bisphenol A, in water samples. The separation and detection of the analytes were performed by high-performance liquid chromatography with diode array detection. These contaminants are considered hazardous to human health and other living beings. Thus, the development of an analytical method to determine these compounds is of great interest. The extraction parameters were evaluated using multivariate and univariate optimization techniques. The optimum conditions for the method were 3 h of extraction time, 20 min of desorption with 300 μL of acetonitrile and methanol (50:50, v/v) and the addition of 5% w/v sodium chloride to the sample. The analytical figures of merit showed good results with linear correlation coefficients higher than 0.99, relative recoveries of 72–125%, inter-day precision (n = 3) of 4–18% and intra-day precision (n = 9) of 1–21%. The limit of detection was 0.3–5.5 μg L−1, and the limit of quantification was 0.8–15 μg L−1. This article is protected by copyright. All rights reserved



Determination of multiple antibiotics in leafy vegetables using QuEChERS–UHPLC–MS/MS

2017-11-14T03:20:21.516339-05:00

A modified quick, easy, cheap, effective, rugged and safe method was established for simultaneous extraction and cleanup of multiple antibiotics in leafy vegetables, and ultra high performance liquid chromatography with tandem mass spectrometry was used for analysis. Antibiotics in leafy vegetables were extracted with citric acid/sodium citrate in mixed solvents consisting of acetonitrile/methanol (85:15 v/v) from 10 g of vegetables. Octadecylsilyl and graphitized carbon black were used as dispersant adsorbents. This method was able to effectively extract all of the target antibiotics from leafy vegetables. The average recoveries of 20 antibiotics ranged from 57 to 91%. The limits of detection were 0.33–2.92 μg/kg. The developed method subsequently demonstrated its selectivity, sensitivity, and reliability for detecting multiple antibiotics in 15 samples. Antibiotic residues in vegetables have attracted great concern with respect to human health. It is recommended that standards should be established for antibiotic residues in vegetables to ensure food safety. This article is protected by copyright. All rights reserved



Determination of the clean-up efficiency of the solid-phase extraction of rosemary extracts: Application of full-factorial design in hyphenation with Gaussian peak fit function

2017-11-14T02:50:25.432789-05:00

We present a novel method for the quantitative determination of the clean-up efficiency to provide a calculated parameter for peak purity through iterative fitting in conjunction with design of experiments. Rosemary extracts were used and analyzed before and after solid-phase extraction using a self-fabricated mixed-mode sorbent based on poly(N-vinylimidazole/ethylene glycol dimethacrylate). Optimization was performed by variation of washing steps using a full three-level factorial design and response surface methodology. Separation efficiency of rosmarinic acid from interfering compounds was calculated using an iterative fit of Gaussian-like signals and quantifications were performed by the separate integration of the two interfering peak areas. Results and recoveries were analyzed using Design-Expert® software and revealed significant differences between the washing steps. Optimized parameters were considered and used for all further experiments. Furthermore, the solid-phase extraction procedure was tested and compared with commercial available sorbents. In contrast to generic protocols of the manufacturers, the optimized procedure showed excellent recoveries and clean-up rates for the polymer with ion exchange properties. Finally, rosemary extracts from different manufacturing areas and application types were studied to verify the developed method for its applicability. The cleaned-up extracts were analyzed by liquid chromatography with tandem mass spectrometry for detailed compound evaluation to exclude any interference from co-eluting molecules. This article is protected by copyright. All rights reserved



Qualitative analysis of flavors and fragrances added to tea by using GC–MS

2017-11-14T00:52:24.068908-05:00

A precise identification method was developed to identify the flavors and fragrances added to tea matrix artificially using gas chromatography with mass spectrometry and gas chromatography with quadrupole time-of-flight mass spectrometry. The proposed method was based on the corresponding “three-column retention indices, two exact mass numbers, one mass spectrum matching degree” database of 40 kinds of common flavors and fragrances. The intra-day and the inter-day relative standard deviation of the retention indices were less than 0.048 and 0.093%, respectively. The accuracy of exact mass was between 0.15 and 6.22 ppm. And the validation of the created database was performed by analyzing the tea samples. Thus, the proposed method is suitable for the precise identification of the flavors and fragrances added to tea matrix artificially without standard substances as a reference. This article is protected by copyright. All rights reserved



Rapid determination of ginkgolic acids in Ginkgo biloba kernels and leaves by direct analysis in real time mass spectrometry

2017-11-14T00:20:38.25016-05:00

A novel method on basis of direct analysis in real time integrated with mass spectrometry was established and applied into rapid determination of ginkgolic acids in Ginkgo biloba kernels and leaves. Instrument parameter settings were optimized to obtain the sensitive and accurate determination of ginkgolic acids. At the sample introduction speed of 0.2 mm/s, high intensity of [M–H]– ions for ginkgolic acids were observed in the negative ion mode by utilization of high purity helium gas at 450°C. 2 μL methanol extract of Ginkgo biloba kernels or leaves dropped on the surface of Quick-Strip module was analyzed after solvent evaporated to dryness. A series of standard solutions of ginkgolic acid 13:0 in the range of 2 to 50 mg/L were analyzed with a correlation coefficient r = 0.9981 and relative standard deviation (n = 5) from 12.5 to 13.7%. The limit of detection was 0.5 mg/L. The results of direct analysis in real time mass spectrometry were in agreement with those observed by thermochemolysis gas chromatography. The proposed method demonstrated significant potential in the application of the high throughput screening, rapid analysis for ginkgolic acids in dietary supplements. This article is protected by copyright. All rights reserved



Metabolic profile of Kudiezi injection in rats by UHPLC coupled with Fourier transform ion cyclotron resonance mass spectrometry

2017-11-13T06:21:45.281065-05:00

In this study, a reliable and sensitive ultra high performance liquid chromatography coupled with Fourier transform ion cyclotron resonance mass spectrometry method was developed for the systematic study of the metabolic profile of Kudiezi injection in rat plasma, bile, urine and feces after intravenous administration of a single dose. The chromatographic separation was performed on an Agilent Eclipse Plus C18 column (4.6 mm × 50 mm, 1.8 μm) and the identification of prototype components and metabolites was achieved on a Bruker Solarix 7.0T ultra-high resolution spectrometer in negative ion mode. Results indicated that a total of 76 constituents including 29 prototype compounds and 47 metabolites (10 phase I metabolites and 37 phase II metabolites) were tentatively identified. And the metabolic pathways of these prototype compounds including hydroxylation, dehydrogenation, glucuronidation and sulfate conjugation. In conclusion, the developed method with high resolution and sensitivity was effective for screening and identification of prototypes and metabolites of Kudiezi injection in vivo. Moreover, these results would provide significant information for further pharmacokinetic and pharmacological research of Kudiezi injection in vivo. This article is protected by copyright. All rights reserved



Modified dispersive liquid-phase microextraction based on sequential injection solidified floating organic drop combined with HPLC for the determination of phenobarbital and phenytoin

2017-11-13T02:10:26.169926-05:00

A modified dispersive liquid phase microextraction based on sequential injection solidified floating organic drop was developed for simultaneous separation/preconcentration of trace amounts of phenobarbital and phenytoin. The important factors affecting on the extraction recovery including pH, the volume of extraction solvent, ionic strength and the number of injections were investigated and optimized by Box–Behnken design and desirability function. Under the optimum experimental conditions, the calibration graph was linear in the concentration range of 1.0–300.0 μg L−1 (r2 = 0.997) for phenobarbital and 2.0–400.0 μg L−1 (r2 = 0.996) for phenytoin. The limit of detection and limit of quantification were 0.35 and 1.2 μg L−1 for phenobarbital and 0.65 and 2.2 μg L−1 for phenytoin, respectively. The relative standard deviation for six replicate determinations at 10 μg L−1 was 3.3 and 4.1% for phenobarbital and phenytoin, respectively. The developed method was successfully applied to the determination of phenobarbital and phenytoin in urine and plasma samples. This article is protected by copyright. All rights reserved



Development of a capillary electrophoresis method for the determination of the chiral purity of dextromethorphan by a dual selector system using quality by design methodology

2017-11-13T01:50:42.543864-05:00

Dextromethorphan is a centrally acting antitussive drug, while its enantiomer levomethorphan is an illicit drug with opioid analgesic effects. As capillary electrophoresis has been proven as an ideal technique for enantiomer analysis, the present study was conducted in order to develop a capillary-electrophoresis-based limit test for levomethorphan. The analytical target profile was defined that the method should be able to determine levomethorphan with acceptable precision and accuracy at the 0.1 % level. From initial scouting experiments, a dual selector system consisting of sulfated β-cyclodextrin and methyl-α-cyclodextrin was identified. The critical process parameters were evaluated in a fractional factorial resolution VI design followed by a central composite face centered design and Monte Carlo simulations for defining the design space of the method. The selected working conditions consisted of a 30/40.2 cm, 50 μm id fused-silica capillary, 30 mM sodium phosphate buffer, pH 6.5, 16 mg/mL sulfated β-cyclodextrin and 14 mg/mL methyl-α-cyclodextrin at 20°C and 20 kV. The method was validated according to ICH guideline Q2(R1) and applied to the analysis of a capsule formulation. Furthermore, the apparent binding constants between the enantiomers and the cyclodextrins as well as complex mobilities were determined to understand the migration behavior of the analytes. This article is protected by copyright. All rights reserved



Synthesis of thermo-responsive bovine hemoglobin imprinted nanoparticles by combining ionic liquid immobilization with aqueous precipitation polymerization

2017-11-12T08:50:28.324993-05:00

Surface molecular imprinting over functionalized nanoparticles has proved to be an effective approach for construction of artificial nanomaterials for protein recognition. Herein, we report a strategy for synthesis of core–shell protein-imprinted nanoparticles by the functionalization of nano-cores with ionic liquids followed by aqueous precipitation polymerization to build thermo-responsive imprinted polymer nano-shells. The immobilized ionic liquids can form multiple interactions with the protein template. The polymerization process can produce thermo-reversible physical crosslinks, which are advantageous to enhancing imprinting and facilitating template removal. With bovine hemoglobin as a model template, the imprinted nanoparticles showed temperature-sensitivity in both dispersion behaviors and rebinding capacities. Compared with the ionic-liquid-modified core nanoparticles, the imprinted particles exhibited greatly increased selectivity and two orders of magnitude higher binding affinity for the template protein. The imprinted nanoparticles achieved relatively high imprinting factor up to 5.0 and specific rebinding capacity of 67.7 mg/g, respectively. These nanoparticles also demonstrated rapid rebinding kinetics and good reproducibility after five cycles of adsorption–regeneration. Therefore, the presented approach may be viable for fabrication of high-performance protein-imprinted nanoparticles with temperature-sensitivity. This article is protected by copyright. All rights reserved



Detection of 13 mycotoxins in feed using modified QuEChERS with dispersive magnetic materials and UHPLC–MS/MS

2017-11-10T09:20:48.492992-05:00

An analytical method for the simultaneous determination of 13 mycotoxins in feed by magnetic dispersive solid-phase extraction combined with ultra high performance liquid chromatography and tandem mass spectrometry was developed. The samples were extracted with acetonitrile/water (80:20, v/v, containing 3% acetic acid), and separated by centrifugation after salting-out, and then treated with magnetic adsorbents to remove interferences. The separation of target mycotoxins was performed on an ACQUITY UPLC HSS T3 column using a mobile phase consisting of 1 mmol/L ammonium acetate with 0.1% formic acid and methanol by gradient elution. Good linearities for the 13 mycotoxins were achieved with correlation coefficients over 0.99, and the recoveries of mycotoxins were in the range of 89.3–112.6% at spiking at levels of 5, 20 and 100 μg/kg, with relative standard deviations of 0.9–10.4%. Based on the functional magnetic materials (MDN@Fe3O4, PSA@Fe3O4, ZrO2@Fe3O4) applied in dispersive solid-phase extraction, the pretreatment process is more convenient and it is beneficial to reduce the experimental cost by reusing the recycled magnetic materials. It is a simple, rapid and environmentally friendly analytical method for the determination of mycotoxins in feed. This article is protected by copyright. All rights reserved



Preparation and characterization of a novel molecularly imprinted polymer for the separation of glycyrrhizic acid

2017-11-10T04:31:09.524086-05:00

Molecularly imprinted polymers of glycyrrhizic acid were prepared by solution polymerization using glycyrrhizic acid as the template molecule, N-vinypyrrolidone as functional monomer, N,N-methylene bisacrylamide as cross-linker and ascorbic acid and hydrogen peroxide as initiators. Focused on the adsorption capacity and separation degree of the polymer to glycyrrhizic acid, the effects of the monomers, crosslinker and initiators were investigated and optimized. Finally, the structure of the polymer was characterized by using Fourier transform infrared spectroscopy and scanning electron microscopy. To obtain objective results, non-imprinted molecular polymers prepared under the same conditions were also characterized. The adsorption quantity of the polymer was measured by high-performance liquid chromatography. Under the optimum conditions, the maximum adsorption capacity of glycyrrhizic acid approached 15 mg/g, and the separation degree was as high as 2.5. The adsorption kinetics could be well described by a pseudo-first-order model, while the thermodynamics of the adsorption process could be described by the Langmuir model. This article is protected by copyright. All rights reserved



Flow injection gas chromatography with sulfur chemiluminescence detection for the analysis of total sulfur in complex hydrocarbon matrixes

2017-11-10T02:20:40.979239-05:00

A fast and reliable analytical technique for the determination of total sulfur levels in complex hydrocarbon matrices is introduced. The method employed flow injection technique using a gas chromatograph as a sample introduction device and a gas phase dual-plasma sulfur chemiluminescence detector for sulfur quantification. Using the technique described, total sulfur measurement in challenging hydrocarbon matrices can be achieved in less than 10 s with sample-to-sample time of less than 2 min. The high degree of selectivity and sensitivity towards sulfur compounds of the detector offers the ability to measure low sulfur levels with a detection limit in the range of 20 ppb (w/w) S. The equimolar response characteristic of the detector allows the quantitation of unknown sulfur compounds and simplifies the calibration process. Response is linear over a concentration range of five orders of magnitude, with a high degree of repeatability. The detector's lack of response to hydrocarbons enables direct analysis without the need for time-consuming sample preparation and chromatographic separation processes. This flow injection based sulfur chemiluminescence detection technique is ideal for fast analysis or trace sulfur analysis. This article is protected by copyright. All rights reserved



Quantitative determination of acidic hydrolysis products of Chemical Weapons Convention related chemicals from aqueous and soil samples using ion-pair solid phase extraction and in-situ butylation

2017-11-09T05:20:22.378792-05:00

Chemical warfare agents such as organophospshorus nerve agents, mustard agents, and psychotomimetic agent like 3-quinuclidinylbenzilate degrade in the environment and form acidic degradation products the analysis of which is difficult under normal analytical conditions. In the present work a simultaneous extraction and derivatization method in which the analytes are butylated followed by gas chromatography and mass spectrometric identification of the analytes from aqueous and soil samples was carried out. The extraction was carried out using ion-pair solid-phase extraction with tetrabutylammonium hydroxide followed by gas chromatography with mass spectrometry in the electron ionization mode. Various parameters such as optimum concentration of the ion-pair reagent, pH of the sample, extraction solvent, type of ion pair reagent were optimized. The method was validated for various parameters such as linearity, accuracy, precision, limit of detection and quantification. The method was observed to be linear from 1–1000 ng/mL range in selected ion monitoring mode. The extraction recoveries were in the range of 85–110% from the matrixes with the limit of quantification for alkyl phosphonic acids at 1 ng/mL, thiodiglycolic acid at 20 ng/mL and benzilic acid at 50 ng/mL with intraday and interday precisions below 15%. The developed method was applied for the samples prepared in the scenario of challenging inspection. This article is protected by copyright. All rights reserved



High-throughput LC–MS/MS method with 96-well plate precipitation for the determination of arotinolol and amlodipine in a small volume of rat plasma: Application to a pharmacokinetic interaction study

2017-11-08T07:50:55.029603-05:00

A rapid, sensitive and selective liquid chromatography with tandem mass spectrometry method was developed and fully validated for the simultaneous quantification of arotinolol and amlodipine in rat plasma. Two internal standards were introduced with metoprolol as the internal standard of arotinolol and (S)-amlodipine-d4 as the internal standard of amlodipine. The analytes were isolated from 50.0 μL plasma samples by a simple protein precipitation using acetonitrile. The chromatographic separation was achieved in 5 min on a C18 column. The mobile phase consisted of phase A 5% methanol and phase B 95% methanol (both containing 0.5% formic acid and 5 mM ammonium acetate) and was delivered in gradient elution at 0.300 mL/min. Quantification was performed in multiple-reaction-monitoring mode with the transition m/z 372.1  316.1 for arotinolol, m/z 268.2  116.2 for metoprolol, m/z 409.1  238.1 for amlodipine and m/z 413.1  238.1 for (S)-amlodipine-d4. Linearity was obtained over the range of 0.200–40.0 ng/mL for arotinolol (r2 = 0.9988) and 0.500–100 ng/mL for amlodipine (r2 = 0.9985) in rat plasma. The validated data have met the acceptance criteria in FDA guideline. This method was successfully applied to a pharmacokinetic interaction study in rats, and the results indicated that there was no significant drug–drug interaction between arotinolol and amlodipine. This article is protected by copyright. All rights reserved



Validated thin-layer chromatographic method for the identification and monitoring of the effect of the extraction method on the yield and phytochemical constituents of Egyptian Withania somnifera leaves

2017-11-08T06:20:43.806114-05:00

A sensitive, reliable, simple and rapid thin-layer chromatographic method has been developed for routine analysis of withanolide S content for the purpose of quality control assessment of chemotype III of W. somnifera. The new method was used first to compare the accumulation of withanolide S in different parts of the plant, which was found to be the highest in the leaves extract (0.21% w/w). Secondly to investigate different extraction parameters that improve the extraction efficiency of withanolides from the leaves using conventional and ultrasound-assisted extraction methods. The extraction efficiency was expressed via total withanolide content (Twc) and withanolide S content. This article is protected by copyright. All rights reserved



In vitro screening and isolation of human aromatase inhibitors from Cicer arietinum by a novel continuous online method combining chromatographic techniques

2017-11-08T06:20:26.555105-05:00

Ultrafiltration liquid chromatography with mass spectrometry can efficiently and rapidly screen and identify ligands from the seeds of Cicer arietinum for human aromatase. Using this method, we identified 11 major compounds, including organic acids, organic acid glycosides, flavone glycosides, isoflavones, and isoflavone glycosides, as potent human aromatase inhibitors. A continuous online method, including pressurized liquid extraction, countercurrent chromatography, and preparative liquid chromatography, was developed for scaling up the production of these compounds with high purity and efficiency. The bioactivity of the separated compounds was assessed by an in vitro enzyme inhibition assay. This novel approach using a combination of ultrafiltration liquid chromatography with mass spectrometry and pressurized liquid extraction with countercurrent chromatography and preparative liquid chromatography as well as an in vitro enzyme inhibition assay could be applied to efficiently screen and isolate human aromatase inhibitors from complex samples and to the large-scale production of functional food and nutraceutical ingredients. This article is protected by copyright. All rights reserved



Facile and versatile strategy to prepare magnetic molecularly imprinted particles based on the coassembly of magnetic nanoparticles and amphiphilic random copolymers

2017-11-07T09:21:01.459252-05:00

Magnetic molecularly imprinted polymer nanoparticles for bisphenol A were prepared by coassembling magnetic nanoparticles and amphiphilic random copolymers. Under optimized conditions, bisphenol A as template molecules, magnetic molecularly imprinted polymer particles with regular morphology, small size, good monodispersity and high content of OA-Fe3O4 were prepared by the coassembly method using P(MMA-co-MAA) with monomer ratio of 9:1. These magnetic molecularly imprinted polymer particles could be rapidly collected by an external magnet within 1 min. The saturated adsorption capacity of the magnetic molecularly imprinted polymer for bisphenol A was 201.5 mg/g, and the imprinting factor was 2.5. The separation factors for bisphenol A to β-estradiol, estriol and diethylstilbestrol was 3.1, 2.9 and 3.7, respectively. Unlike assembling amphiphilic copolymer in the selective solvent, the coassembly process was simple and rapid. Therefore, the present work provided a facile and versatile approach to construct magnetic molecularly imprinted polymer nanoparticles under mild conditions. This article is protected by copyright. All rights reserved



Recent Applications of GC with high-resolution MS

2017-11-07T05:22:43.220748-05:00

Gas chromatography coupled to high-resolution mass spectrometry is a powerful analytical method that combines excellent separation power of gas chromatography with improved identification based on an accurate mass measurement. These features designate gas chromatography with high-resolution mass spectrometry as the first choice for identification and structure elucidation of unknown volatile and semi-volatile organic compounds. Gas chromatography with high-resolution mass spectrometry quantitative analyses were previously focused on the determination of dioxins and related compounds using magnetic sector type analyzers, a standing requirement of many international standards. The introduction of a quadrupole high-resolution time-of-flight mass analyzer broadened interest in this method and novel applications were developed, especially for multi-target screening purposes. This review is focused on the development and the most interesting applications of gas chromatography with high-resolution mass spectrometry towards analysis of environmental matrices, biological fluids and food safety since 2010. The main attention is paid to various approaches and applications of gas chromatography with high-resolution mass spectrometry for non-target screening to identify contaminants and to characterize the chemical composition of environmental, food and biological samples. The most interesting quantitative applications, where a significant contribution of gas chromatography with high-resolution mass spectrometry over the currently used methods is expected, will be discussed as well. This article is protected by copyright. All rights reserved



Synthesis and application of a novel solid-phase extraction adsorbent for the multiresidue analysis of insecticides in water

2017-11-06T06:21:50.144229-05:00

A new solid-phase adsorbent was synthesized for the simultaneous enrichment of multiple classes of trace insecticides (neonicotinoids, organophosphates, fiproles and organochlorines) in water. The adsorbent was spherical with a diameter, surface area, average pore volume and pore size of ∼5 μm, 341 m2/g, 0.092 m3/g and 2.22 nm, respectively. Extraction conditions were optimized, including water pH and the type and volume of the rinsing and eluting solvents. After extraction, target insecticides were analyzed by gas chromatography with mass spectrometry and high-performance liquid chromatography with tandem mass spectrometry. The recovery of neonicotinoids ranged from 63.0 to 124%, except for clothianidin (40.1–52.9%). Recoveries of organophosphates, fiproles and organochlorines were in the ranges of 37.0–102, 64.0–101 and 42.0–69.3%, respectively. Relative standard deviations were < 20% except for profenofos (5.1–30%) and method detection limits were 1.8–12.7 ng/L, suggesting that the precision and accuracy of the developed method were viable. At environmentally relevant concentrations, the new adsorbent achieved comparable recoveries of target insecticides to hydrophilic-lipophilic balance adsorbent while providing an additional advantage by further reducing matrix effects. Field water samples from the Pearl River in Guangzhou, China were analyzed, and the frequent detection of neonicotinoids raises concerns about their aquatic risk. This article is protected by copyright. All rights reserved



Identification of Salvia species using HPLC combined with chemical pattern recognition analysis

2017-11-06T06:20:37.616045-05:00

Salvia miltiorrhiza, also known as Danshen, is a widely used traditional Chinese medicine for the treatment of cardiovascular diseases and haematological abnormalities. The root and rhizome of S. przewalskii and S. yunnanensis have been found as substitutes for S. miltiorrhiza in the market. In this study, the chemical information of 14 major compounds in S. miltiorrhiza and its substitutes were determined using a high-performance liquid chromatography method. Stepwise discriminant analysis was adopted to select the characteristic variables. Partial least squares discriminant and hierarchical cluster analysis were performed to classify S. miltiorrhiza and its substitutes. The results showed that all of the samples were correctly classified both in partial least squares discriminant analysis and hierarchical cluster analysis based on the four compounds (caffeic acid, rosmarinic acid, salvianolic acid B and salvianolic acid A). This method can not only distinguish S. miltiorrhiza and its substitutes, but also classify S. przewalskii and S. yunnanensis. The method can be applied for the quality assessment of S. miltiorrhiza and identification of unknown samples. This article is protected by copyright. All rights reserved



Chemical profiling and quantification of ShenKang injection, a systematic quality control strategy using ultra high performance liquid chromatography with Q Exactive hybrid quadrupole orbitrap high-resolution accurate mass spectrometry

2017-11-06T05:57:42.847756-05:00

ShenKang injection is traditional Chinese medicine used to treat chronic renal failure in China. It is a compound preparation that consists of four herbs: Rhubarb, Salvia miltiorrhiza, Safflower and Radix Astragali. We developed an ultra high pressure liquid chromatography coupled with Q Exactive hybrid quadrupole-orbitrap high resolution accurate mass spectrometry tandem mass spectrometry method to analyze its chemical compositions, and a total of 90 compounds were identified from ShenKang injection. Among them, 19 major compounds were unambiguously detected by comparing with reference standards. Meanwhile, 13 representative compounds selected as quality control markers were simultaneously quantified in ShenKang injection samples. Chromatographic separation was accomplished on a Waters ACQUITY HPLC® HSS C18 column using gradient elution. The method was validated with respect to linearity, sensitivity, accuracy and precision, reproducibility and stability. And the validated method was successfully applied for simultaneous determination of 13 bioactive compounds in ShenKang injection from ten batches of samples by liquid chromatography with mass spectrometry. The results were analyzed by principal components analysis method, and three compounds had a significant relationship with the quality control of ShenKang injection. This research established a rapid and reliable method for the integrating quality control, including qualitation and quantification of ShenKang injection. This article is protected by copyright. All rights reserved



Metabonomics study of the effects of traditional Chinese medicine formula Ermiaowan on hyperuricemic rats

2017-11-03T01:50:32.974692-05:00

To explore the global mechanism of Ermiaowan on hyperuricemia regulation, the holistic function of Ermiaowan for hyperuricemia in rats was firstly assessed by the urinary metabonomics method which was based on ultra high performance liquid chromatography with electrospray ionization quadrupole time-of-flight mass spectrometry. The urinary targeted metabonomics approach combined with the serum biochemical analysis and histological assay was conducted to verify the research result. As a result, the significant differences in metabolic profiles were observed from Ermiaowan-treated group, model group and healthy control group by using multivariate statistical approaches. The 20 therapeutic related metabolites were identified in response to the therapeutic effects of Ermiaowan, which were mainly associated with purine metabolism, pyrimidine metabolism, tryptophan metabolism, tricarboxylic acid cycle and tyrosine metabolism. In addition, the urinary targeted metabonomics study showed that Ermiaowan can better restore the disturbed pathways than Phellodendri cortex and Atractylodis rhizome. The biochemical assay and histopathological assay confirmed that Ermiaowan could significantly reduce uric acid and fibrosis areas of kidney. These results provided new insights into the mechanism of Ermiaowan on hyperuricemia. This article is protected by copyright. All rights reserved



Quality evaluation of raw and processed Crataegi Fructus by color measurement and fingerprint analysis

2017-11-03T01:21:54.572926-05:00

Crataegi Fructus and its processed products have been used as a traditional medicine for a long time, and numerous active components are responsible for their curative effects. However, a comprehensive and fast method for the quality control of its processed products is still lacking. In this study, two analytical methods based on color measurements and fingerprint analysis were established. In the color measurements, the color values (L*, a*, b*) of the peel and flesh of Crataegi Fructus were evaluated spectrophotometrically. Based on the results, a color reference range was established using percentiles, and the standard color difference value (∆E) was established using the median color values. Then, the color values of Crataegi Fructus and its processed products were analyzed using Bayes linear discriminant analysis and mathematical functions were built in order to predict the degree of processing. Moreover, high-performance liquid chromatography fingerprint analysis was performed on a Hibar C18 column, and a high-performance liquid chromatography fingerprint pattern was obtained, from which nine peaks were identified. Chemometric methods were successfully applied to differentiate raw and processed Crataegi Fructus. This article is protected by copyright. All rights reserved



Screening and identification of potential hypoglycemic components in Zeng Ye Tang by high-performance liquid chromatography coupled with tandem quadrupole time-of-flight mass spectrometry

2017-11-03T01:21:04.475105-05:00

Zeng Ye Tang, a famous prescription consisting of Xuanshen, Maidong and Shengdi (5:4:4), has been used in China for a long time to treat diabetes caused by excessive heat with yin deficiency. Although many studies have investigated the pharmacological effects of Zeng Ye Tang, the compounds responsible for its hypoglycemic effect have not been identified. In this study, 50 compounds in Zeng Ye Tang were identified by high-performance liquid chromatography coupled with tandem quadrupole time-of-flight mass spectrometry. From these 50 compounds, nine cell-interacted compounds were identified by biospecific cell extraction using 3T3-L1 adipocytes. Moreover, nine potential active compounds that could be released into the blood were also acquired through serum pharmacochemical analysis in normal and diabetic rats after administration with Zeng Ye Tang. According to the established quantitative analytical method of nine constituents by high-performance liquid chromatography, six shared prototype constituents (catalpol/harpagide/p-coumaric acid/harpagoside/angoroside C/cinnamic acid 75.56:19.74:1.00:15.11:20.36:7.65), were screened and verified to exert remarkable hypoglycemic activity on type 2 diabetic mice. In conclusion, the six shared constituents may responsible for the hypoglycemic activity of Zeng Ye Tang. This article is protected by copyright. All rights reserved



Preparation and characterization of molecularly-imprinted polymers for extraction of sanshool acid amide compounds followed by their separation from pepper oil resin derived from Chinese prickly ash (Zanthoxylum bungeanum)

2017-11-02T07:51:01.380398-05:00

Molecularly imprinted polymers were prepared using the molecular structure analogs of sanshool as template molecule, 2-vinylpyridine and β-cyclodextrin as double functional monomers, ethylene dimethacrylate as cross linker, and azobisisobutyronitrile as initiator. The structural characteristics of the polymers were determined by Fourier-transform infrared spectroscopy and scanning electron microscopy. Dynamic adsorption and isothermal adsorption were also investigated. The molecularly imprinted polymers were used to prepare a molecularly imprinted solid-phase extraction column in order to separate acid amide components from pepper oil resin derived from Chinese prickly ash (Zanthoxylum bungeanum). After eluting, the percentage of acid amide components was enhanced to 92.40±1.41% compared with 23.34±1.21% in the initial pepper oil resin, indicating good properties of purification of molecularly imprinted polymers and potential industrial application. This article is protected by copyright. All rights reserved



Determination of cannabinoids from a surrogate hops matrix using multiple reaction monitoring gas chromatography with triple quadrupole mass spectrometry

2017-11-02T07:20:26.925374-05:00

Cannabinoids are the primary bioactive constituents of Cannabis sativa and Cannabis indica plants. In this work, gas chromatography in conjunction with triple quadrupole mass spectrometry in multiple reaction monitoring mode was explored for determination of cannabinoids from a surrogate hops matrix. Gas chromatography with mass spectrometry is a reasonable choice for the analysis of these compounds; however, such methods are susceptible to false positives for Δ9-tetrahydrocannabinol, due to decarboxylation of Δ9-tetrahydrocannabinolic acid, its acid precursor, in the hot injection port. To avoid this transformation, the carboxyl group of Δ9-tetrahydrocannabinolic acid was protected through a silylation reaction. Multiple reaction monitoring transitions for both unmodified and silylated cannabinoids were developed and the fragmentation pathways of the different species were assigned. Precision and accuracy were evaluated for cannabinoids spiked into hops at different levels. The developed methods provided good linearity (R2 > 0.99) for all the cannabinoids with a linear range from 0.15 to 20 mg/L, and with limits of detection in the orders of low- to mid-picogram on column. The recoveries for the cannabinoids were generally between 75 and 120%. Precisions (< 6% coefficient of variation) were within acceptable ranges. This article is protected by copyright. All rights reserved



Preparation of highly hydrophilic magnetic nanoparticles with anion-exchange ability and their application for the extraction of nonsteroidal anti-inflammatory drugs in environmental samples

2017-11-02T07:15:28.701099-05:00

Diallyldimethylammonium chloride modified magnetic nanoparticles were synthesized by the “thiol-ene” click chemistry reaction. Diallyldimethylammonium chloride rendered the material plenty of quaternary ammonium groups, and thus the excellent aqueous dispersibility and anion-exchange capability. The novel material was then used as the magnetic solid-phase extraction sorbent to extract eight non-steroidal anti-inflammatory drugs from water samples. Combined with high-performance liquid chromatography and ultraviolet detection, under the optimal conditions, the developed method exhibited wide linearity ranges (1–1000, 2–1000 and 5–1000 ng mL−1) with recoveries of 88.0–108.6% and low limits of detection (0.3–1.5 ng mL−1). Acceptable precision was obtained with satisfactory intra-day and inter-day relative standard deviations of 0.4–4.4% (n = 3) and 1.1–5.5% (n = 3), respectively. Batch-to-batch reproducibility was acceptable with relative standard deviations < 9.7%. The hydrophilic magnetic nanoparticle featured with quaternary ammonium groups showed high analytical potential for acidic analytes in environmental water samples. This article is protected by copyright. All rights reserved



CE method for analyzing Salmonella typhimurium in water samples

2017-10-31T07:51:07.015038-05:00

Salmonella typhimurium is commonly described as a food-borne pathogen. However, natural and drinking water are known to be important sources for the transmission of this pathogen in developing and developed countries. The standard method to determine Salmonella is laborious and many false positives are detected. To solve this, the present work was focused on the development of a capillary zone electrophoresis method coupled to ultraviolet detection for determination of Salmonella typhimurium in water (mineral and tap water). Separations were performed in less than 11 minutes using 4.5 mM Tris (hydroxymethyl)-aminomethane, 4.5 mM boric acid and 0.1 mM ethylene diamine tetraacetate (pH 8.4) with 0.1% v/v poly ethylene oxide as separation buffer. The precision of the method was evaluated in terms of repeatability obtaining a relative standard deviation of 10.5%. Using the proposed method Salmonella typhimurium could be separated from other bacteria that could be present in water such as Escherichia coli. Finally, the proposed methodology was applied to determine Salmonella typhimurium in tap and mineral water. This article is protected by copyright. All rights reserved



Isolation and purification of alkaloids from lotus leaves by ionic-liquid-modified high-speed countercurrent chromatography

2017-10-31T07:50:31.075475-05:00

An effective high-speed countercurrent chromatography method was successfully established by using ionic liquids as the modifier of the two-phase solvent system. Adding a small amount of ionic liquids significantly shortens the separation time and improves the separation efficiency. The conditions of ionic-liquid-modified high-speed countercurrent chromatography including solvent systems, types and content of added ionic liquids, and ionic liquids post-treatment were investigated. The established method was successfully applied to separate alkaloids from lotus leaves using a two-phase solvent system composed of petroleum ether/ethyl acetate/methanol/water/[C4mim][BF4] (1:5:1:5:0.15, v/v). Four alkaloids pronuciferine (1.7 mg), N-nornuciferine (4.3 mg), nuciferine (3.1 mg), and roemerine (2.1 mg) were obtained with the purities of 90.53, 92.25, 99.86 and 98.63%, respectively from 100 mg crude extract of lotus leaves. The results indicated that ionic-liquid-modified high-speed countercurrent chromatography method was suitable for alkaloid separation from lotus leaves and would be a promising method for the separation of alkaloids from other natural products. This article is protected by copyright. All rights reserved



Quantitative fingerprinting based on the limited-ratio quantified fingerprint method for an overall quality consistency assessment and antioxidant activity determination of Lianqiao Baidu pills using HPLC with a diode array detector combined with chemometric methods

2017-10-31T00:20:27.59018-05:00

Lianqiao Baidu pills are a widely used herbal medicinal preparation that were analyzed to develop a quality consistency technique. The characteristic fingerprints of 28 batches of Lianqiao Baidu pill samples were established at five wavelengths and simultaneously assessed by using a limited-ratio quantified fingerprint method using 15 marker compounds. The principal component analysis and fingerprinting results were compared, and the qualitative classification of the samples by principal component analysis agreed with their quantitative evaluation by the limited-ratio quantified fingerprint method. Furthermore, the antioxidant activities of the samples were surveyed and determined using a 2,2-diphenyl-1-picrylhydrazyl radical-scavenging approach. A relationship between the common peaks in the fingerprints and the antioxidant activities was established using a partial least squares model. The relationship can be used both to determine the antioxidant activities of the Lianqiao Baidu pill preparations in vitro and as a reference for the selection of active constituents for sample quality classification. The classification results for the samples based on principal component analysis agreed with the quantitative evaluation by the limited-ratio quantified fingerprint method, which demonstrated that the method can be applied to the holistic quality control of traditional Chinese medicine and herbal preparations. This article is protected by copyright. All rights reserved



Development of a microextraction by packed sorbent with GC–MS method for the quantification of nitroexplosives in aqueous and fluidic biological samples

2017-10-30T23:50:33.059304-05:00

A new method for quantification of 12 nitroaromatic compounds, including 2,4,6-trinitrotoluene, its metabolites and Tetryl, with microextraction by packed sorbent followed by gas chromatography and mass spectrometric detection in environmental and biological samples is developed. The microextraction device employs 4 mg of C18 silica sorbent inserted into a microvolume syringe for sample preparation. Several parameters capable of influencing the microextraction procedure, namely, the number of extraction cycles, washing solvent, volume of washing solvent, elution solvent, and volume of eluting solvent and pH of matrix, were optimized. The developed method produced satisfactory results with excellent values of coefficient of determination (R2 > 0.9804) within the established calibration range. The extraction yields were satisfactory for all analytes (> 89.32%) for aqueous samples and (> 87.45%) for fluidic biological samples. The limits of detection values lie in the range of 14–828 pg/mL. This article is protected by copyright. All rights reserved



Simultaneous determination of isomeric substituted anilines by imidization with benzaldehyde and GC–MS

2017-10-30T08:20:34.610522-05:00

The chromatographic separation of several isomeric anilines is a challenging issue. Herein, a simple method for the simultaneous determination of four groups of isomeric primary aromatic amines, including chloroanilines, methylanilines, methoxylanilines and dimethylanilines, was presented. In this method, all of the 15 primary aromatic amines were easily transformed into the corresponding imine derivative by treatment with benzaldehyde under mild conditions. The formed isomeric imine derivatives were completely separated on a commercial capillary gas chromatography column. The effects of several derivatization parameters were investigated and optimized. Linearity in the optimized method ranged from 0.050 to 50 μg/mL with the squared correlation coefficients (R2) between 0.9981 and 0.9999. Reasonable reproducibility was obtained, with the intraday relative standard deviation (N = 5) ranging from 0.89 to 4.57 % and interday relative standard deviation ranging from 2.26 to 7.69% at the concentration of 5.0 μg/mL. The developed method has been successfully applied to determine these isomeric aromatic amines in real samples. This article is protected by copyright. All rights reserved



Simultaneous analysis of carbohydrates, polyols and amines in urine samples using chemical ionization gas chromatography with tandem mass spectrometry

2017-10-30T00:50:46.864903-05:00

A simple method for the simultaneous derivatization of carbohydrates, polyols, amines and amino acids using hexamethyldisilazane and N,O-bis(trimethylsilyl)trifluoroacetamide was developed. This method allows the direct derivatization of urine samples without sample pretreatment before derivatization. The method was successfully used for analysis of the selected metabolites in urine samples of healthy individuals and neonates suffering from galactosemia. The limits of detection by positive chemical ionization gas chromatography with tandem mass spectrometry analysis were in the range of 1.0 mgL-1 for mannitol to 4.7 mgL-1 for glucose. This article is protected by copyright. All rights reserved



Ion-pair-based hollow-fiber liquid-phase microextraction combined with high-performance liquid chromatography for the simultaneous determination of urinary benzene, toluene, and styrene metabolites

2017-10-30T00:50:43.924788-05:00

In the current study, a novel technique for extraction and determination of trans,trans-muconic acid, hippuric acid, and mandelic acid was developed by means of ion-pair-based hollow fiber liquid-phase microextraction in the three-phase mode. Important factors affecting the extraction efficiency of the method were investigated and optimized. These metabolites were extracted from 10 mL of the source phase into a supported liquid membrane containing 1-octanol and 10% w/v of Aliquat 336 as the ionic carrier followed by high-performance liquid chromatography analysis. The organic phase immobilized in the pores of a hollow fiber was back-extracted into 24 μL of a solution containing 3.0 mol L−1 sodium chloride placed inside the lumen of the fiber. A very high preconcentration of 212–440 fold, limit of detection of 0.1–7 μg L−1, and relative recovery of 87–95% were obtained under the optimized conditions of this method. The relative standard deviation values for within-day and between-day precisions were calculated at 2.9–8.5 and 4.3–11.2%, respectively. The method was successfully applied to urine samples from volunteers at different work environments. The results demonstrated that the method can be used as a sensitive and effective technique for the determination of the metabolites in urine. This article is protected by copyright. All rights reserved



Separation of selenium species and their sensitive determination in rice samples by ion-pairing reversed-phase liquid chromatography with inductively coupled plasma tandem mass spectrometry

2017-10-30T00:50:35.232876-05:00

A highly sensitive method was developed for the simultaneous separation and determination of organic and inorganic selenium species in rice by ion-pairing reversed-phase chromatography combined with inductively coupled plasma tandem mass spectrometry. To achieve a good separation of these species, a comparison between anion-exchange chromatography and ion-pairing reversed-phase chromatography was performed. The results indicated that ion-pairing reversed-phase chromatography was more suitable due to better separation and higher sensitivity for all analytes. In this case, a StableBond C18 column proved to be more robust or to have a better resolution than other C18 columns, when 0.5 mM tetrabutylammonium hydroxide and 10 mM ammonium acetate at pH 5.5 were used as the mobile phase. Moreover, an excellent sensitivity was obtained in terms of interferences by means of tandem mass spectrometry in the hydrogen mode. The detection limits were 0.02–0.12 μg L–1, and recoveries of five selenium species were 75–114%, with relative standard deviations ≤ 9.4%. This method was successfully applied to the analysis of rice samples. Compared with previous studies, the proposed method not only gave comparable results when used for measuring selenium-enriched rice, but it can provide greater sensitivity for the detection of low concentrations of selenium species in rice. This article is protected by copyright. All rights reserved



Liquid chromatography coupled with hybrid ion trap time-of-flight mass spectrometry method for the determination of caulophine in rat bio-samples and its pharmacokinetic study after intragastric and intraperitoneal administration

2017-10-29T23:50:23.204523-05:00

A rapid and precise liquid chromatography coupled with hybrid ion trap/time-of-flight mass spectrometry method to detect and quantify caulophine and its possible active metabolites in rat plasma and urine was developed. Samples were prepared by plasma protein precipitation combined with a liquid-liquid extraction method. The separation was carried out on an InertSustain® C18 column with a mobile phase comprising methanol and 0.1% aqueous formic acid solution. The analysis was complete in 20 min with a flow rate of 0.4 mL/min. Taspine was used as the internal standard. Mass spectrometric detection was conducted with hybrid ion trap/time-of-flight equipped with electrospray ionization in the positive ion mode. The calibration curves of caulophine were linear over the concentration ranges of 0.002–0.20 μg/mL for plasma and 0.005–0.50 μg/mL for urine with the correlation coefficients greater than 0.998 in both cases. The method was successfully used to investigate the pharmacokinetics and bioavailability in rat plasma and urine samples after intragastric and intraperitoneal administration of caulophine sodium salt. This article is protected by copyright. All rights reserved



Dispersive micro-solid-phase extraction combined with online preconcentration by capillary electrophoresis for the determination of glycopyrrolate stereoisomers in rat plasma

2017-10-28T04:50:22.493531-05:00

A simple and sensitive analytical method for four isomers of glycopyrrolate in rat plasma was developed using cation-selective exhaustive injection-sweeping cyclodextrin-modified electrokinetic chromatography (CSEI-Sweeping-CDEKC) for on-line enrichment combined with dispersive micro-solid-phase extraction pretreatment. The CSEI-Sweeping-CDEK was conducted on an uncoated fused silica capillary (40.2 cm × 75 μm) with an applied voltage of –20 kV. The electrophoretic analysis was carried out in 30 mM phosphate solution at pH 2.0 containing 20 mg/mL sulfated-β-cyclodextrin and 5% acetonitrile. Under these optimized conditions, the detection limit for racemic glycopyrrolate was found to be 2.0 ng/mL and this method could increase 495-fold detection sensitivity compared with traditional injection method. Additionally, the parameters that affected the extraction efficiency of dispersive micro-solid-phase extraction were also examined systematically. The glycopyrrolate isomers in rat plasma samples as low as 0.0625 μg/mL were able to be separated and detected by capillary electrophoresis with the aid of CSEI-sweeping. The findings of this study show that the dispersive micro-solid-phase extraction pretreatment coupled with CSEI-Sweeping-CDEK is a rapid and convenient method for analyzing glycopyrrolate isomers in rat plasma. This article is protected by copyright. All rights reserved



Highly selective and efficient imprinted polymers based on carboxyl-functionalized magnetic nanoparticles for the extraction of gallic acid from pomegranate rind

2017-10-27T01:50:38.63869-05:00

With the combined surface imprinting technique and immobilized template strategy, molecularly imprinted magnetic nanoparticles were successfully prepared and coupled with high-performance liquid chromatography to selectively separate and determine gallic acid from the pomegranate rind. On the surface of carboxyl-functionalized magnetic nanospheres, thin imprinting shells were formed using dopamine as monomer and crosslinker. The characteristics, polymerization conditions, and adsorption performances of the resultant nanomaterials were investigated in detail. In addition of good crystallinity, satisfactory magnetism, and uniform morphology of the obtained polymers, they had rapid binding kinetics, high adsorption capacity, and favorable reusability. In the mixed solution of four hydroxybenzoic acids, the prepared nanomaterials have an excellent selectivity to gallic acid with an imprinting factor of as high as 17.5. Therefore, the polymers have great potentials in specific extraction and enrichment of gallic acid from the complex natural resources. This article is protected by copyright. All rights reserved



Construction of a novel electrochemical sensor based on molecularly imprinted polymers for the selective determination of chlorpyrifos in real samples

2017-10-26T08:22:47.881953-05:00

We present a novel electrochemical sensor based on an electrode modified with molecularly imprinted polymers for the detection of chlorpyrifos. The modified electrode was constructed by the synthesis of molecularly imprinted polymers by a precipitation method then coated on a glassy carbon electrode. The surface morphology of the modified electrode was characterized by using field-emission scanning electron microscopy. The performance of the imprinted sensor was thoroughly investigated by using cyclic voltammetry and differential pulse voltammetry. The imprinted electrochemical sensor displayed high repeatability, stability and selectivity towards the template molecules. Under the optimal experimental conditions, the peak current response of the imprinted electrochemical sensor was linearly related to the concentration of chlorpyrifos over the range 1 × 10−10–1 × 10−5 mol L−1 with a limit of detection of 4.08 × 10−9 mol L−1 (S/N = 3). Furthermore, the proposed molecularly imprinted electrochemical sensor was applied to the determination of chlorpyrifos in the complicated matrixes of real samples with satisfactory results. Therefore, the molecularly imprinted polymers based electrochemical sensor might provide a highly selective, rapid, and cost-effective method for chlorpyrifos determination and related analysis. This article is protected by copyright. All rights reserved



Mobile phase effects on the retention on polar columns with special attention to the dual hydrophilic interaction – reversed-phase liquid chromatography mechanism: A review

2017-10-26T07:21:02.537182-05:00

Hydrophilic interaction liquid chromatography on polar columns in aqueous–organic mobile phases has become increasingly popular for the separation of many biologically important compounds in chemical, environmental, food, toxicological and other samples. In spite of many new applications appearing in literature, the retention mechanism is still controversial. This review addresses recent progress in understanding of the retention models in hydrophilic interaction liquid chromatography. The main attention is focused on the role of water, both adsorbed by the column and contained in the bulk mobile phase. Further, the theoretical retention models in the isocratic and gradient elution modes are discussed. The dual hydrophilic interaction liquid chromatography reversed-phase retention mechanism on polar columns is treated in detail, especially with respect to the practical use in one- and two-dimensional liquid chromatography separations. This article is protected by copyright. All rights reserved



Simultaneous determination of niacin and pyridoxine at trace levels by using diode array high-performance liquid chromatography and liquid chromatography with quadrupole time-of-flight tandem mass spectrometry

2017-10-26T03:52:01.936819-05:00

A highly sensitive and simple diode-array high-performance liquid chromatography and liquid chromatography with quadrupole time-of-flight tandem mass spectrometry method was developed for the simultaneous determination of niacin and pyridoxine in pharmaceutical drugs, tap water and wastewater samples. To determine the in vivo behavior of niacin and pyridoxine, analytes were subjected to simulated gastric conditions. The calibration plots of the diode-array high-performance liquid chromatography and liquid chromatography with quadrupole time-of-flight tandem mass spectrometry method showed good linearity over a wide concentration range with close to 1.0 correlation coefficients for both analytes. The limit of detection/limit of quantitation values for liquid chromatography quadrupole time-of-flight tandem mass spectrometry analysis were 1.98/6.59 and 1.3/4.4 μg L−1 for niacin and pyridoxine, respectively, while limit of detection/limit of quantitation values for niacin and pyridoxine in high-performance liquid chromatography analysis were 3.7/12.3 and 5.7/18.9 μg L−1, respectively. Recovery studies were also performed to show the applicability of the developed methods, and % recovery values ​​were found to be between 90–105% in tap water and 94–97% in wastewater for both analytes. The method was also successfully applied for the qualitative and quantitative determination of niacin and pyridoxine in drug samples. This article is protected by copyright. All rights reserved



Online hyphenation of extraction, Sephadex LH-20 column chromatography, and high-speed counter-current chromatography: A highly efficient strategy for the preparative separation of andrographolide from Andrographis paniculata in a single step

2017-10-26T03:51:58.121482-05:00

A novel isolation strategy, on-line hyphenation of ultrasonic extraction, Sephadex LH-20 column chromatography combined with high-speed counter-current chromatography, was developed for pure compounds extraction and purification. Andrographolide from Andrographis paniculata was achieved only in a single step purification protocol via the present strategy. The crude powder was ultrasonic extracted and extraction was pumped into Sephadex LH-20 column directly to cut the non-target fractions followed by the second dimensional high-speed counter-current chromatography, hyphenated by a six-port valve equipped at the post-end of Sephadex LH-20 column, for the final purification. The results yielded andrographolide with the amount of 1.02 mg and a purity of 98.5% in a single step, indicating that the present method is effective to harvest target compound from medicinal plant. This article is protected by copyright. All rights reserved



Isolation of ellagic acid from pomegranate peel extract by hydrophobic interaction chromatography using graphene oxide grafted cotton fiber adsorbent

2017-10-26T03:51:46.289526-05:00

Ellagic acid, a natural polyphenol, was isolated from pomegranate peel extract by hydrophobic interaction using graphene oxide grafted cotton fiber as a stationary adsorbent. The grafted graphene oxide moieties served as hydrophobic interaction binding sites for ellagic acid adsorption. The graphene oxide grafted cotton fiber was made into a membrane-like sheet in order to complete ellagic acid purification by using a binding–elution mode. The effects of operational parameters, such as the composition of the binding buffer/elution buffer, buffer pH and buffer concentration, on the isolation process were investigated. It was found that 5 mmol/L sodium carbonate aqueous solution is a proper binding buffer, and sodium hydroxide aqueous solution ranging from 0.04 to 0.06 mol/L is a suitable elution solution for ellagic acid purification. Under the optimized condition, the purity of ellagic acid increased significantly from 7.5% in the crude extract to 75.0–80.0%. The pH value was found to be a key parameter that determines the adsorption and desorption of ellagic acid. No organic solvent is involved in the entire purification process. Thus, a simple and environmentally friendly method is established for ellagic acid purification using a graphene oxide modified biodegradable and bio-sourced fibrous adsorbent. This article is protected by copyright. All rights reserved



Qualitative analysis of multiple compounds in raw and prepared Semen Cassiae coupled with multiple statistical strategies

2017-10-25T09:52:11.33759-05:00

In China, Semen Cassiae is used clinically to improve eyesight, relieve constipation, and to treat headache and dizziness. Prepared Semen Cassiae is obtained by stir-frying raw Semen Cassiae until it turned dark brown, micro dilatancy and overflow aroma. After processing, the therapeutic effects change—the purgation effect is alleviated and the hepatoprotective effect is enhanced. To explore the changes in chemical compositions of Semen Cassiae after processing and clarify the material basis of the changed therapeutic effects, an ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry coupled with automated data analysis software and statistical strategy was developed. As a result, 53 compounds in raw Semen Cassiae and 43 compounds in prepared Semen Cassiae were found, a total of 55 chemical compounds were identified. Principle component analysis and t-test were processed by Markerview 1.2.1 software. Finally, 39 peaks were found to be the main contributors to the significant difference (p < 0.05) between raw and prepared Semen Cassiae. Compared with raw Semen Cassiae, 19 peaks showed a higher intensity in prepared Semen Cassiae, while the content of 20 compounds in prepared Semen Cassiae was lower, most of which belonged to naphthopyrones glycosides and anthraquinone glycosides. This article is protected by copyright. All rights reserved



Rapid preparation of methyltrimethoxy-modified magnetic mesoporous silica as an effective solid-phase extraction adsorbent

2017-10-25T09:52:01.258168-05:00

A time-saving method was applied to synthesize methyltrimethoxy-modified magnetic mesoporous silica with or without p-toluenesulfonic acid as the catalyst for magnetic solid-phase extraction. The synthesized materials were systematically characterized. Results demonstrated that methyltrimethoxy modified magnetic mesoporous silica with p-toluenesulfonic acid as the catalyst has a relatively smaller aperture and extreme hydrophobicity (water contact angle of 135°). To evaluate the feasibility of these prepared materials as effective adsorbents, it was combined with gas chromatography and electron capture detection to determine 26 polychlorinated biphenyls in environmental water. The result revealed that methyltrimethoxy modified magnetic mesoporous silica with p-toluenesulfonic acid as the catalyst had the best extraction efficiency and recovery. Under the optimized extracted conditions, the proposed method showed good linearity within the concentration range of 5 to 200 ng L−1 with correlation coefficients of 0.9969 to 0.9999. The LOD and LOQ based on signal-to-noise ratios of 3 and 10 were in the range of 0.16 to 0.91 ng L−1 and 0.52 to 3.0 ng L−1, respectively. The PCB concentrations in environmental water samples were successfully determined using the developed method. PCB008 and PCB110 were 4.05 and 8.52 ng L−1 in Red-Star lake water (Hubei Province, China), respectively. This article is protected by copyright. All rights reserved



Simultaneous determination of furfural and its degradation products, furoic acid and maleic acid, in transformer oil by the reversed-phase vortex-assisted liquid–liquid microextraction followed by HPLC

2017-10-25T08:50:26.348145-05:00

To explore why the use of furfural as a transformer oil-paper insulation aging characteristic is problematic in real world application, we developed a method for the simultaneous determination of furfural, furoic acid and maleic acid in transformer oil by reversed-phase vortex-assisted liquid–liquid microextraction combined with high-performance liquid chromatography. The conditions for the proposed method were optimized, and the obtained extract can be directly analyzed by high-performance liquid chromatography. The detection limits (S/N = 3) of the method ranged from 1.0 to 4.6 μg·L−1, the enrichment factors for furfural, furoic acid, maleic acid and fumaric acid were 4.6, 25.1, 15.6 and 17.5, respectively, and the recoveries rate for three analytes (fumaric acid was undetected) range from 82.0 to 110.6%. The contents of furfural, furoic acid and maleic acid resulted from accelerated aging of transformer insulation oil-paper were measured using the present method for the first time, and the aging samples were analyzed by liquid chromatography with mass spectrometry for the identification of furoic acid and maleic acid in the aging transformer oil samples. Using the optimal method, the target products of samples at different aging time were tracked and measured. This article is protected by copyright. All rights reserved



A cationic β-cyclodextrin as a dynamic coating for the separation of proteins in capillary electrophoresis

2017-10-25T07:50:20.149211-05:00

A cationic cyclodextrin was used as dynamic coating for the capillary electrophoresis of a model mixture of proteins (i.e., ubiquitin, α-lactoglobulin, cytochrome-c, and myoglobin) as positively charged species in a fused silica capillary. An interesting feature of the coating is that by simple adjustment of the concentration of cyclodextrin added into the background electrolyte, a neutral or positively charged surface, which was beneficial in preventing protein adsorption at the inner capillary wall surface, was obtained. This is the first demonstration of a dynamic coating that yielded a neutral surface for protein separations in capillary electrophoresis. Based on electro-osmotic flow measurements, addition of 0.05 to 0.10 mg/mL quaternary β-cyclodextrin in a low pH electrolyte resulted to a neutral or positive surface (undetectable to very slow anodic electro-osmotic flow). The coating approach afforded the electrophoretic separation of the mixture of proteins at positive polarity with good repeatability and separation performance. Short Communication This article is protected by copyright. All rights reserved



Comparative Study on Chemical Components and Anti-inflammatory Effects of Panax notoginseng Flower Extracted by Water and Methanol

2017-10-25T07:20:29.070537-05:00

Methanol and water are commonly used solvents for chemical analysis and traditional decoction, respectively. In the present study, a high-performance liquid chromatography with ultraviolet detection method was developed to quantify 11 saponins in Panax notoginseng Flower extracted by aqueous and methanol solutions, and chemical components and anti-inflammatory effects of these two extracts were compared. The separation of 11 saponins, including notoginsenoside Fc and ginsenoside Rc, was well achieved on a Zorbax SB C18 column. This developed method provides an adequate linearity (r2 > 0.999), repeatability (RSD < 4.26 %), inter- and intra- day variations (RSD < 3.20 %) with recovery (94.7–104.1%) of 11 saponins concerned. Our data indicated that saponin biotransformation in PNF was found, when water was used as the extraction solvent, but not methanol. Specifically, the major components of Panax notoginseng Flower, ginsenosides Rb1, Rc, Rb2, Rb3 and Rd, can be near completely transformed to the minor components, gypenoside XVII, notoginsenoside Fe, ginsenoside Rd2, notoginsenoside Fd and ginsenoside F2, respectively. Total protein isolated from Panax notoginseng Flower is responsible for this saponin biotransformation. Additionally, methanol extracts exerted the stronger anti-inflammatory effects than water extracts in lipopolysaccharide-induced RAW264.7 cells. This difference in anti-inflammatory action might be attributed to their chemical difference of saponins. This article is protected by copyright. All rights reserved



Separation of structurally related primary aliphatic amines using hydrophilic interaction chromatography with fluorescence detection after postcolumn derivatization with o-phtaldialdehyde/mercaptoethanol

2017-10-23T03:22:41.381494-05:00

The retention behavior of primary aliphatic amines (homologous series of aliphatic alkyl amines and cycloalkyl amines) and positional isomers of alkylamines in the hydrophilic interaction chromatography mode was studied. The study was carried out on a TSKgel Amide-80 column followed by post-column derivatization with fluorescence detection to describe the retention mechanism of tested compounds. The effect of chromatographic conditions including column temperature, acetonitrile content in the mobile phase, mobile phase pH (ranging from 3.5 to 6.8) and salt concentration in the mobile phase was investigated. The final mobile phase consisted of acetonitrile and solution of 20 mM potassium formate pH 3.5 in ratio 80:20 (v/v). The analyses were carried out at mobile phase flow rate of 1.0 mL/min and the column temperature of 20°C. The developed method was fully validated in terms of linearity, sensitivity (limit of detection and limit of quantification), accuracy and precision according to International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use guidelines. The proposed new methods were proved to be highly sensitive, simple and rapid, and were successfully applied to the determinations of isopropylamine, cyclohexylamine and cyclopropylamine in relevant active pharmaceutical ingredients. This article is protected by copyright. All rights reserved



Optimizing separations in online comprehensive two-dimensional liquid chromatography

2017-11-23T09:29:21.673858-05:00

Online comprehensive two-dimensional liquid chromatography has become an attractive option for the analysis of complex nonvolatile samples found in various fields (e.g. environmental studies, food, life, and polymer sciences). Two-dimensional liquid chromatography complements the highly popular hyphenated systems that combine liquid chromatography with mass spectrometry. Two-dimensional liquid chromatography is also applied to the analysis of samples that are not compatible with mass spectrometry (e.g. high-molecular-weight polymers), providing important information on the distribution of the sample components along chemical dimensions (molecular weight, charge, lipophilicity, stereochemistry, etc.). Also, in comparison with conventional one-dimensional liquid chromatography, two-dimensional liquid chromatography provides a greater separation power (peak capacity). Because of the additional selectivity and higher peak capacity, the combination of two-dimensional liquid chromatography with mass spectrometry allows for simpler mixtures of compounds to be introduced in the ion source at any given time, improving quantitative analysis by reducing matrix effects. In this review, we summarize the rationale and principles of two-dimensional liquid chromatography experiments, describe advantages and disadvantages of combining different selectivities and discuss strategies to improve the quality of two-dimensional liquid chromatography separations.



Immobilized-enzyme reactors integrated with capillary electrophoresis for pharmaceutical research

2017-11-23T09:28:46.352568-05:00

Enzymes play an essential role in many aspects of pharmaceutical research as drug targets, drug metabolizers, enzyme drugs and more. In this specific field, enzyme assays are required to meet a number of specific requirements, such as low cost, easy automation, and high reliability. The integration of an immobilized-enzyme reactor to capillary electrophoresis represents a unique approach to fulfilling these criteria by combining the benefits of enzyme immobilization, that is, increased stability and repeated use, as well as the minute sample consumption, short analysis time, and efficient analysis provided by capillary electrophoresis. In this review, we summarize, analyze, and discuss published works where pharmaceutically relevant enzymes were used to prepare capillary electrophoresis-integrated immobilized-enzyme reactors in an online manner. The presented assays are divided into three distinct groups based on the drug–enzyme relationship. The first, more extensively studied group employs enzymes that are considered to be therapeutic targets, the second group of assays present tools to assess drug metabolism and the third group assesses enzyme drugs. Furthermore, we examine various methods of enzyme immobilization and their implications for assay properties.



Adding a new separation dimension to MS and LC–MS: What is the utility of ion mobility spectrometry?

2017-11-23T09:23:18.696025-05:00

Ion mobility spectrometry is an analytical technique known for more than 100 years, which entails separating ions in the gas phase based on their size, shape, and charge. While ion mobility spectrometry alone can be useful for some applications (mostly security analysis for detecting certain classes of narcotics and explosives), it becomes even more powerful in combination with mass spectrometry and high-performance liquid chromatography. Indeed, the limited resolving power of ion mobility spectrometry alone can be tackled when combining this analytical strategy with mass spectrometry or liquid chromatography with mass spectrometry. Over the last few years, the hyphenation of ion mobility spectrometry to mass spectrometry or liquid chromatography with mass spectrometry has attracted more and more interest, with significant progresses in both technical advances and pioneering applications. This review describes the theoretical background, available technologies, and future capabilities of these techniques. It also highlights a wide range of applications, from small molecules (natural products, metabolites, glycans, lipids) to large biomolecules (proteins, protein complexes, biopharmaceuticals, oligonucleotides).



Nanostructured gemini-based supramolecular solvent coupled with ultrasound-assisted back extraction as a preconcentration step before GC–MS

2017-11-22T10:55:41.036873-05:00

Liquid-phase microextraction based on gemini-based supramolecular solvent was successfully applied as a preconcentration step before gas chromatography with mass spectrometry. To eliminate the interferences of gemini surfactant, the analytes were back-extracted into an immiscible organic solvent in the presence of ultrasonic sound waves. Three phthalate esters (di-n-butyl-, butylbenzyl-, bis(2-ethylhexyl)-, and di-n-octyl phthalatic esters) were used as target analytes. The effective parameters on extraction efficiency of the target analytes (i.e., the amount of surfactant and volume of propanol as major components making up the supramolecular solvent, ionic strength, hexane volume, and ultrasound time) were investigated and optimized by a one-variable-at-a-time method. Under the optimum conditions, the preconcentration factors of the analytes were in the range of 95–182. The linear dynamic range of 0.05–200.00 μg/L with a correlation of determination of (R2) ≥ 0.9935 was obtained. The proposed method had an excellent limit of detection (S/N = 3) of 0.01 for di-n-octyl and 0.02 μg/L for butylbenzyl- and di-n-butyl-phthalatic ester. Good relative recoveries in the range of 85.7–105.2% guaranteed the accuracy of the amount of phthalates distinguished in the nonspiked samples.



Sol–gel/nanoclay composite as a sorbent for microextraction in packed syringe combined with corona discharge ionization ion mobility spectrometry for the determination of diazinon in water samples

2017-11-20T03:13:05.924168-05:00

In this work, the microextraction in packed syringe technique combined with corona discharge ion mobility spectrometry was used for determining diazinon in water samples. A new porous composite of nanoclay and polysiloxane was prepared using a sol–gel process. An amount of 2.0 mg of the sorbent was packed in a 250 μL syringe and used for extraction. A volume of 2 mL of the sample was passed through the sorbent bed, and the entrapped analyte was eluted by 25 μL of methanol. Important parameters influencing the extraction performance were investigated. Under optimum experimental conditions, the detection limit for diazinon was 0.07 ng/mL. The intra- and inter-day relative standard deviations were 5.0 and 12.3%, respectively. The calibration curve was linear in the concentration range from 0.2 to 20.0 ng/mL (r2 = 0.999). The applicability of the method was demonstrated by analyzing spiked real water samples and the spiking recoveries were in the range of 95 to 106%.



Screening and separation of α-amylase inhibitors from Solanum nigrum with amylase-functionalized magnetic graphene oxide combined with high-speed counter-current chromatography

2017-11-20T02:10:37.250539-05:00

A screening method using α-amylase-functionalized magnetic graphene oxide combined with high-speed counter-current chromatography was proposed and utilized to screen and separate α-amylase inhibitors from extract of Solanum nigrum. The α-amylase-functionalized magnetic graphene oxide was characterized and found to demonstrate satisfactory structure, magnetic response (24.5 emu/g), and reusability (retained 90% of initial activity after five cycles). The conditions for the screening with α-amylase functionalized magnetic graphene oxide were optimized and set at pH 7.0 and 25°C. As a result, two potent flavonoid compounds, apigenin-7-O-glucuronide (1) and astragalin (2), were separated and collected through high-speed counter-current chromatography and subjected to high-performance liquid chromatography analysis with purity higher than 90% (according to HPLC data), which were identified as α-amylase inhibitors. These results suggested that utilization of α-amylase functionalized magnetic graphene oxide in the rapid screening and isolation bioactive compounds from complex natural products is a feasible and environmentally friendly method.



The role of graphene-based sorbents in modern sample preparation techniques

2017-11-20T02:10:27.60421-05:00

The application of graphene-based sorbents in sample preparation techniques has increased significantly since 2011. These materials have good physicochemical properties to be used as sorbent and have shown excellent results in different sample preparation techniques. Graphene and its precursor graphene oxide have been considered to be good candidates to improve the extraction and concentration of different classes of target compounds (e.g., parabens, polycyclic aromatic hydrocarbon, pyrethroids, triazines, and so on) present in complex matrices. Its applications have been employed during the analysis of different matrices (e.g., environmental, biological and food). In this review, we highlight the most important characteristics of graphene-based material, their properties, synthesis routes, and the most important applications in both off-line and on-line sample preparation techniques. The discussion of the off-line approaches includes methods derived from conventional solid-phase extraction focusing on the miniaturized magnetic and dispersive modes. The modes of microextraction techniques called stir bar sorptive extraction, solid phase microextraction, and microextraction by packed sorbent are discussed. The on-line approaches focus on the use of graphene-based material mainly in on-line solid phase extraction, its variation called in-tube solid-phase microextraction, and on-line microdialysis systems.



Advanced online mass spectrometry detection of proteins separated by capillary isoelectric focusing after sequential injection

2017-11-17T04:33:03.178377-05:00

Capillary isoelectric focusing hyphenated with mass spectrometry detection, following the sequential injection of the carrier ampholytes and the sample zone, is highly efficient for the characterization of proteins. The main advantage of the sequential injection protocol is that ampholytes, with pH ranges, which are not supposed to cover the isoelectric points of the sample components, can be used for separation. The method then allows online mass spectrometry detection of separated analytes either in the absence (substances that have left the pH gradient) or in the presence of low-level ampholytes (substances that are migrating within the pH gradient). The appearance of the substances within, or outside the pH gradient depends on, e.g., the composition of the ampholytes (broad or narrow pH range) or on the composition of electrolyte solutions. The experiments performed in coated capillaries (with polyvinyl alcohol or with polyacrylamide) show that the amount and the injection length of the ampholytes influence the length of the pH gradient formed in the capillary.



How to model temporal changes in nontargeted metabolomics study? A Bayesian multilevel perspective

2017-11-17T03:40:54.844812-05:00

Analysis of time series data addresses the question on mechanisms underlying normal physiology and its alteration under pathological conditions. However, adding time variable to high-dimension, collinear, noisy data is a challenge in terms of mining and analysis. Here, we used Bayesian multilevel modeling for time series metabolomics in vivo study to model different levels of random effects occurring as a consequence of hierarchical data structure. A multilevel linear model assuming different treatment effects with double exponential prior, considering major sources of variability and robustness to outliers was proposed and tested in terms of performance. The treatment effect for each metabolite was close to zero suggesting small if any effect of cancer on metabolomics profile change. The average difference in 964 signals for all metabolites varied by a factor ranging from 0.8 to 1.25. The inter-rat variability (expressed as a coefficient of variation) ranged from 3–30% across all metabolites with median around 10%, whereas the inter-occasion variability ranged from 0–30% with a median around 5%. Approximately 36% of metabolites contained outlying data points. The complex correlation structure between metabolite signals was revealed. We conclude that kinetics of metabolites can be modeled using tools accepted in pharmacokinetics type of studies.



Electrophoretic deposition strategy for the fabrication of highly stable functionalized silica nanoparticle coatings onto nickel-titanium alloy wires for selective solid-phase microextraction

2017-11-17T03:36:39.368616-05:00

A new strategy for the immobilization of phenyl-functionalized silica nanoparticles onto nickel-titanium alloy wires is presented. The homogeneous and compact silica nanoparticle coating was achieved on the hydrothermally treated nickel-titanium wires with large surface area by electrophoretic deposition, and followed by self-assembled modification of phenyltrichlorosilane. Coupled to high-performance liquid chromatography with ultraviolet detection, the extraction performance of the fabricated fiber was evaluated using typical aromatic compounds in direct-immersion mode of solid-phase microextraction. Due to its high extraction efficiency and good selectivity for ultraviolet filters, the novel fiber was employed to investigate the key factors affecting the extraction of ultraviolet filters. Under the optimized conditions, the proposed method presented linear ranges from 0.05 to 300 μg/L with correlation coefficients higher than 0.999 and limits of detection from 0.005 to 0.058 μg/L. Relative standard deviations were below 4.3 and 5.6% for intraday and interday analyses at the spiking level of 50 μg/L ultraviolet filters with the single fiber, respectively. The proposed method was successfully applied to the selective concentration and sensitive detection of target ultraviolet filters from environmental water samples. Furthermore, the developed fiber can be used at least 200 times, and fabricated in a precisely controllable manner.



Poly(ionic liquids)-coated stainless-steel wires packed into a polyether ether ketone tube for in-tube solid-phase microextraction

2017-11-17T03:35:35.405993-05:00

An in-tube solid-phase microextraction device was developed by packing poly(ionic liquids)-coated stainless-steel wires into a polyether ether ketone tube. An anion-exchange process was performed to enhance the extraction performance. Surface properties of poly(ionic liquids)-coated stainless-steel wires were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The extraction device was connected to high-performance liquid chromatography equipment to build an online enrichment and analysis system. Ten polycyclic aromatic hydrocarbons were used as model analytes, and important conditions including extraction time and desorption time were optimized. The enrichment factors from 268 to 2497, linear range of 0.03–20 μg/L, detection limits of 0.010–0.020 μg/L, extraction and preparation repeatability with relative standard deviation less than 1.8 and 19%, respectively were given by the established online analysis method. It has been used to detect polycyclic aromatic hydrocarbons in environmental samples, with the relative recovery (5, 10 μg/L) in the range of 85.1–118.9%.



Emerging materials for sample preparation

2017-11-13T04:42:56.81184-05:00

This review provides an update on the implementation of emerging materials as sorbents for sample preparation in combination with chromatographic separation. We have focused on recent applications of metal–organic frameworks, layered double hydroxides, porous carbons obtained from polymers or biomass precursors, and silicates (clays and zeolites). The review is directed toward the strategies followed by the authors to engineer suitable supports enabling the application of materials with unconventional size and shape as high-performance sorbents to explore new boundaries in sample pretreatment in manual or automated modes.



Number of theoretical plates achievable by a toroidal capillary electrophoresis system

2017-11-13T04:41:15.647563-05:00

The ability of a method and instrument to separate very similar compounds is related to the “plate number,” a number indicating performance. The resolution between two neighboring peaks is proportional to the square root of the plate number. Currently available commercial capillary electrophoresis instruments easily reach plate numbers of a few million. In the present work, a capillary electrophoresis system with a toroidal platform is proposed and theoretically studied with the goal of extending the achievable plate number. In this new system, electrophoresis occurs in a nonstop continuous circulating mode within a closed loop capillary (toroid). Plate numbers upwards of one billion are theoretically predicted. This could resolve hundreds of unseparated mixtures of stereoisomers and other analytes that remain without a method for their analysis.



Comparative study of cylindrical and parallel-plate electrophoretic separations for the removal of ions and sub-23 nm particles

2017-11-13T04:41:04.665873-05:00

Cylindrical and parallel-plate electrophoretic separations for the removal of ions and sub-23 nm particles were compared in this study. First, COMSOL Multiphysics® software was utilized to simulate the ion and particle trajectories inside both electrophoretic separations. The results show that ions and sub-23 nm particles are removed simultaneously and that all particles can pass through both electrophoretic separations smoothly at a trap voltage of 25 V. The experimental results show that ion losses become smaller with increasing ion flow rates, and ion losses of the cylindrical and parallel-plate electrophoretic separations range from 56.2 to 71.6% and from 43.8 to 59.6%, respectively, at ion flow rates ranging from 1–3 L/min. For the removal of ions and sub-23 nm particles, the collection efficiency of both electrophoretic separations can reach 100%, but the parallel-plate electrophoretic separation requires a lower trap voltage. The particle loss of the parallel-plate electrophoretic separation is under approximately 10%, which is lower than that of the cylindrical electrophoretic separation. In particular, for large particles (800–2500 nm), the particle losses inside the cylindrical electrophoretic separation are approximately two times higher than those inside the parallel-plate electrophoretic separation. The parallel-plate electrophoretic separation is beneficial for the removal of ions and sub-23 nm particles.



Simultaneous analysis by Quadrupole-Orbitrap mass spectrometry and UHPLC-MS/MS for the determination of sedative-hypnotics and sleep inducers in adulterated products

2017-11-13T03:21:46.045669-05:00

Adulterated products are continuously detected in society and cause problems. In this study, we developed and validated a method for determining synthetic sedative-hypnotics and sleep inducers, including barbital, benzodiazepam, zolpidem, and first-generation antihistamines, in adulterated products using Quadrupole-Orbitrap mass spectrometry and ultrahigh performance liquid chromatography with tandem mass spectrometry. In Quadrupole-Orbitrap mass spectrometry analysis, target compounds were confirmed using a combination of retention time, mass tolerance, mass accuracy, and fragment ions. For quantification, several validation parameters were employed using ultrahigh performance liquid chromatography with tandem mass spectrometry. The limit of detection and limit of quantitation was 0.05–53 and 0.17–177 ng/mL, respectively. The correlation coefficient for linearity was more than 0.995. The intra- and interassay accuracies were 86–110 and 84–111%, respectively. Their precision values were evaluated as within 4.0 (intraday) and 10.7% (interday). Mean recoveries of target compounds in adulterated products ranged from 85 to 116%. The relative standard deviation of stability was less than 10.7% at 4°C for 48 h. The 144 adulterated products obtained over 3 years (2014–2016) from online and in-person vendors were tested using established methods. After rapidly screening with Quadrupole-Orbitrap mass spectrometry, the detected samples were quantified using ultrahigh performance liquid chromatography with tandem mass spectrometry. Two of them were adulterated with phenobarbital.



Magnetic molecularly imprinted polymers for recognition and enrichment of polysaccharides from seaweed

2017-11-13T03:21:33.761212-05:00

New magnetic molecularly imprinted polymers with two templates were fabricated for the recognition of polysaccharides (fucoidan and alginic acid) from seaweed by magnetic solid-phase extraction, and the materials were modified by seven types of deep eutectic solvents. It was found that the deep eutectic solvents magnetic molecularly imprinted polymers showed stronger recognition and higher recoveries for fucoidan and alginic acid than magnetic molecularly imprinted polymers, and the deep eutectic solvents-4-magnetic molecularly imprinted polymers had the best effects. The practical recovery of the two polysaccharides (fucoidan and alginic acid) purified with deep eutectic solvents-4-magnetic molecular imprinted polymers in seaweed under the optimal conditions were 89.87, and 92.0%, respectively, and the actual amounts extracted were 20.6 and 18.7 μg/g, respectively. To sum up, the developed method proved to be a novel and promising method for the recognition of complex polysaccharide samples from seaweed.



Enantioseparation of nornicotine in tobacco by ultraperformance convergence chromatography with tandem mass spectrometry

2017-11-13T03:21:15.143088-05:00

Nornicotine, an alkaloid constituent of tobacco, is a precursor to the carcinogen N-nitrosonornicotine that is produced during the curing and processing of tobacco. Accumulating evidence reveals that nornicotine enantiomers have different neurochemical and behavioral effects. In the present study, an accurate and rapid method was developed for the enantioseparation of (R)-(+)-nornicotine and (S)-(−)-nornicotine enantiomers in tobacco by ultra-performance convergence chromatography with tandem mass spectrometry. Chromatographic conditions were investigated to achieve the optimal resolution of two enantiomers. Results indicated that (R)-(+)-nornicotine and (S)-(−)-nornicotine could be separated within 5 min when ammonium hydroxide was added into the cosolvent, and the best resolution (Rs = 4.76) was achieved on a immobilized cellulose tris-(3,5-dichlorophenylcarbamate) chiral stationary phase. The proposed method was validated and was finally applied to analyze the compositions of (R)-(+)-nornicotine and (S)-(−)-nornicotine in three typical types of tobaccos (flue-cured, burley, and oriental). It was found that, enantiomer fraction of nornicotine (the proportion of (S)-(−)-nornicotine in the nornicotine pool) in burley tobacco samples was relatively high and constant compared with flue-cured and oriental tobaccos. The effective and rapid enantioseparation of nornicotine may help the understanding of alkaloid metabolites in different tobacco varieties and may also benefit pharmacological studies of alkaloid enantiomers.



Free amino acids, biogenic amines, and ammonium profiling in tobacco from different geographical origins using microwave-assisted extraction followed by ultra high performance liquid chromatography

2017-11-13T03:15:30.567255-05:00

This work describes a rapid, stable, and accurate method for determining the free amino acids, biogenic amines, and ammonium in tobacco. The target analytes were extracted with microwave-assisted extraction and then derivatized with diethyl ethoxymethylenemalonate, followed by ultra high performance liquid chromatography analysis. The experimental design used to optimize the microwave-assisted extraction conditions showed that the optimal extraction time was 10 min with a temperature of 60°C. The stability of aminoenone derivatives was improved by keeping the pH near 9.0, and there was no obvious degradation during the 80°C heating and room temperature storage. Under optimal conditions, this method showed good linearity (R2 > 0.999) and sensitivity (limits of detection 0.010–0.081 μg/mL). The extraction recoveries were between 88.4 and 106.5%, while the repeatability and reproducibility ranged from 0.48 to 5.12% and from 1.56 to 6.52%, respectively. The newly developed method was employed to analyze the tobacco from different geographical origins. Principal component analysis showed that four geographical origins of tobacco could be clearly distinguished and that each had their characteristic components. The proposed method also showed great potential for further investigations on nitrogen metabolism in plants.



Preparation and evaluation of diblock copolymer-grafted silica by sequential surface initiated-atom transfer radical polymerization for reverse-phase/ion-exchange mixed-mode chromatography

2017-11-09T12:38:15.895451-05:00

A novel approach that involved the grafting of diblock copolymer with two types of monomer onto substrate by sequential surface initiated-atom transfer radical polymerization was proposed to prepare a mixed-mode chromatographic stationary phase. The distinguishing feature of this method is that it can be applied in the preparation of various mixed-mode stationary phases. In this study, a new reverse-phase/ion-exchange stationary phase was prepared by grafting hydrophobic styrene and cationic sodium 4-styrenesulfonate by the proposed approach onto silica surface. The chromatographic properties of the prepared stationary phase were evaluated by the separation of benzene derivatives, anilines, and β-agonists, and by the effect of pH values and acetonitrile content on the retention. Compared with typical RP columns, the prepared stationary phase achieved the better resolution and higher selectivity at a shorter separation time and lower organic content. Moreover, the application of the prepared column was proved by separating widely distributed polar and charged compounds simultaneously.



Development and evaluation of microwave-assisted and ultrasound-assisted methods based on a quick, easy, cheap, effective, rugged, and safe sample preparation approach for the determination of bisphenol analogues in serum and sediments

2017-11-09T12:37:57.846587-05:00

Microwave- and ultrasound-assisted methods based on a quick, easy, cheap, effective, rugged, and safe sample preparation approach followed by high-performance liquid chromatography with tandem mass spectrometry were developed for the simultaneous determination of eight bisphenol analogues in serum and sediment. The developed methods provided satisfactory extraction efficiency for the energy provided by microwaves and ultrasound. Compositions of commercial sorbents (primary secondary amine, MgSO4, octadecyl-modified silica, and graphitized carbon black) were evaluated. The ultrasound-assisted method was suited for serum using primary secondary amine, MgSO4, and octadecyl-modified silica as sorbents and a mixture of hexane and ethyl acetate as extraction solvent. The microwave-assisted method worked better for sediment with tetrahydrofuran and methanol as solvents and primary secondary amine, MgSO4, octadecyl-modified silica, and graphitized carbon black as sorbents. Other experimental parameters, such as extraction temperature and time, were also optimized. The inter- and intraday relative standard deviations ranged from 2.7 to 5.5%. The limits of detection were between 0.1 and 1.0 ng/mL for serum and between 0.1 and 0.5 ng/g dry weight for sediment. The proposed methods were successfully applied to seven sediment and 20 human serum samples. The results showed that the developed methods were practical for the analysis and biomonitoring of bisphenols in sera and sediment.



Core–shell microspheres with porous nanostructured shells for liquid chromatography

2017-11-06T04:48:59.995929-05:00

The development of new stationary phases has been the key aspect for fast and efficient high-performance liquid chromatography separation with relatively low backpressure. Core–shell particles, with a solid core and porous shell, have been extensively investigated and commercially manufactured in the last decade. The excellent performance of core–shell particles columns has been recorded for a wide range of analytes, covering small and large molecules, neutral and ionic (acidic and basic), biomolecules and metabolites. In this review, we first introduce the advance and advantages of core–shell particles (or more widely known as superficially porous particles) against non-porous particles and fully porous particles. This is followed by the detailed description of various methods used to fabricate core–shell particles. We then discuss the applications of common silica core–shell particles (mostly commercially manufactured), spheres-on-sphere particles and core–shell particles with a non-silica shell. This review concludes with a summary and perspective on the development of stationary phase materials for high-performance liquid chromatography applications.



Deep eutectic solvent based magnetic nanofluid in the development of stir bar sorptive dispersive microextraction: An efficient hyphenated sample preparation for ultra-trace nitroaromatic explosives extraction in wastewater

2017-11-03T07:11:12.906172-05:00

A deep eutectic solvent based magnetic nanofluid was coupled with stir bar sorptive dispersive microextraction as a hyphenated sample preparation technique. The neodymium core magnetic stir bar was coated physically with nanofluid of magnetic carbon nanotube nanocomposites and deep eutectic solvents. The prepared nanofluid has magnetic and strong sorbing properties and is compatible with gas chromatography. In this nanofluid, the deep eutectic solvent acts simultaneously as both carrier and stabilizer for magnetic nanotubes. The predominant experimental variables affecting the extraction efficiency of nitroaromatic compounds were evaluated. Under the optimized conditions, the limit of detection and enrichment factor were in the range of 0.2–4.9 ng/L and 852–1480, respectively. The relative standard deviations were between 5.6 and 10.2% (n = 6). Method validation was performed by both spiking–recovery method and comparison of results with other methods. Finally, the proposed method was successfully applied for the extraction and pre-concentration of nitroaromatic explosives in water samples, followed by determination by gas chromatography with micro-electron capture detection.



Characterization of ancient lipids in prehistoric organic residues: Chemical evidence of livestock-pens in rock-shelters since early neolithic to bronze age

2017-11-03T07:11:02.238655-05:00

The characterization of ancient lipids from prehistoric sediments (fumiers) located in a rock-selter has been possible after the optimization of an analytical method based on the microwave-assisted extraction and solid-phase extraction clean-up step and a final derivatization step followed by gas chromatography with mass spectrometry. Eight sterols and two bile acids were detected just in the partially burned and unburned layers of the fumiers (animal organic residues deriving from manure/dung). The relationship between some of these compounds can be used to distinguish the biogenic origin of the samples, concluding that these strata (from Early Neolithic to Late Chalcolithic/Early Bronze Age) can be classified as ruminant residues. Three main periods of activity are observed over a period of 2000 years: one from 3990 ± 40 before present (4530–4410 calibrated before present) to 4100 ± 40 before present (4820–4750/4730–4510/4470–4450 calibrated before present), the second from 4470 ± 40 before present (5300–4970 calibrated before present) to 5490 ± 30 before present (6310–6275/6230–6220 calibrated before present) and the third from 5880 ± 30 before present (6775–6765/6750–6645 calibrated before present) to 6010 ± 30 before present (6940–6780/6765–6755 calibrated before present). Chemical data obtained are in concordance with the previous results obtained in the area.



Critical comparison of the on-line and off-line molecularly imprinted solid-phase extraction of patulin coupled with liquid chromatography

2017-11-02T10:47:17.129162-05:00

Reaching trace amounts of mycotoxin contamination requires sensitive and selective analytical tools for their determination. Improving the selectivity of sample pretreatment steps covering new and modern extraction techniques is one way to achieve it. Molecularly imprinted polymers as selective sorbent for extraction undoubtedly meet these criteria. The presented work is focused on the hyphenation of on-line molecularly imprinted solid-phase extraction with a chromatography system using a column-switching approach. Making a critical comparison with a simultaneously developed off-line extraction procedure, evaluation of pros and cons of each method, and determining the reliability of both methods on a real sample analysis were carried out. Both high-performance liquid chromatography methods, using off-line extraction on molecularly imprinted polymer and an on-line column-switching approach, were validated, and the validation results were compared against each other. Although automation leads to significant time savings, fewer human errors, and required no handling of toxic solvents, it reached worse detection limits (15 versus 6 μg/L), worse recovery values (68.3–123.5 versus 81.2–109.9%), and worse efficiency throughout the entire clean-up process in comparison with the off-line extraction method. The difficulties encountered, the compromises made during the optimization of on-line coupling and their critical evaluation are presented in detail.



Advances in native high-performance liquid chromatography and intact mass spectrometry for the characterization of biopharmaceutical products

2017-11-02T10:41:20.939067-05:00

The characterization of biotherapeutics represents a major analytical challenge. This review discusses the current state-of-the-art in analytical technologies to profile biopharma products under native conditions, i.e., the protein three dimensional conformation is maintained during liquid chromatographic analysis. Native liquid-chromatographic modes that are discussed include aqueous size-exclusion chromatography, hydrophobic interaction chromatography, and ion-exchange chromatography. Infusion conditions and the possibilities and limitations to hyphenate native liquid chromatography to mass spectrometry are discussed. Furthermore, the applicability of native liquid-chromatography methods and intact mass spectrometry analysis for the characterization of monoclonal antibodies and antibody–drug conjugates is discussed.



Photoirradiation surface molecularly imprinted polymers for the separation of 6-O-α-d-maltosyl-β-cyclodextrin

2017-11-02T10:41:08.631363-05:00

Photoirradiation surface molecularly imprinted polymers for the separation of 6-O-α-d-maltosyl-β-cyclodextrin were synthesized using functionalized silica as a matrix, 4-(phenyldiazenyl)phenol as a light-sensitive monomer, and 6-O-α-d-maltosyl-β-cyclodextrin as a template. Fourier transform infrared spectroscopy results indicated that 4-(phenyldiazenyl)phenol was grafted onto the surface of functionalized silica. The obtained imprinted polymers exhibited specific recognition toward 6-O-α-d-maltosyl-β-cyclodextrin. Equilibrium binding experiments showed that the photoirradiation surface molecularly imprinted polymers obtained the maximum adsorption amount of 6-O-α-d-maltosyl-β-cyclodextrin at 20.5 mg/g. In binding kinetic experiments, the adsorption reached saturation within 2 h with binding capacity of 72.8%. The experimental results showed that the adsorption capacity and selectivity of imprinted polymers were effective for the separation of 6-O-α-d-maltosyl-β-cyclodextrin, indicating that imprinted polymers could be used to isolate 6-O-α-d-maltosyl-β-cyclodextrin from a conversion mixture containing β-cyclodextrin and maltose. The results showed that the imprinted polymers prepared by this method were very promising for the selective separation of 6-O-α-d-maltosyl-β-cyclodextrin.



Recent advances in methods for the analysis of protein o-glycosylation at proteome level

2017-11-02T10:40:35.184287-05:00

O-Glycosylation, which refers to the glycosylation of the hydroxyl group of side chains of Serine/Threonine/Tyrosine residues, is one of the most common post-translational modifications. Compared with N-linked glycosylation, O-glycosylation is less explored because of its complex structure and relatively low abundance. Recently, O-glycosylation has drawn more and more attention for its various functions in many sophisticated biological processes. To obtain a deep understanding of O-glycosylation, many efforts have been devoted to develop effective strategies to analyze the two most abundant types of O-glycosylation, i.e. O-N-acetylgalactosamine and O-N-acetylglucosamine glycosylation. In this review, we summarize the proteomics workflows to analyze these two types of O-glycosylation. For the large-scale analysis of mucin-type glycosylation, the glycan simplification strategies including the ‘‘SimpleCell’’ technology were introduced. A variety of enrichment methods including lectin affinity chromatography, hydrophilic interaction chromatography, hydrazide chemistry, and chemoenzymatic method were introduced for the proteomics analysis of O-N-acetylgalactosamine and O-N-acetylglucosamine glycosylation.



Analysis of six active components in Radix tinosporae by nonaqueous capillary electrophoresis with mass spectrometry

2017-10-30T01:46:39.295362-05:00

Nonaqueous capillary electrophoresis with mass spectrometry has advantages for the analysis of active components in herbs. Here, a rapid nonaqueous capillary electrophoresis with mass spectrometry method was developed to separate, identify, and quantify palmatin, columbin, cepharanthine, menisperine, magnoflorine, and 20-hydroxyecdysone in Radix tinosporae. Electrospray ionization MS1-3 spectra of the six components were collected and possible cleavage pathways of main fragment ions were elucidated. The conditions that could affect separation, such as the composition of running buffer and applied voltage, were studied, and the conditions that could affect the mass spectrometry detection, such as the composition and flow rate of sheath liquid, the pressure of nitrogen gas, and the temperature and flow rate of the dry gas, were also optimized. Under the optimized conditions, the correlation coefficient was >0.99. The relative standard deviations of migration time and peak areas were <10%. The recoveries were calculated to be 99.31–107.80% in real samples. It has been demonstrated that the proposed method has good potential to be applied to determine the six bioactive components in Radix tinosporae.



Dispersive admicelle solid-phase extraction based on sodium dodecyl sulfate coated Fe3O4 nanoparticles for the selective adsorption of three alkaloids in Gegen-Qinlian oral liquid before high-performance liquid chromatography

2017-10-30T01:46:28.324404-05:00

A novel dispersive admicelle solid-phase extraction method based on sodium dodecyl sulfate-coated Fe3O4 nanoparticles was developed for the selective adsorption of berberine, coptisine, and palmatine in Gegen-Qinlian oral liquid before high-performance liquid chromatography. Fe3O4 nanoparticles were synthesized by a chemical coprecipitation method and characterized by using transmission electron microscopy. Under acidic conditions, the surface of Fe3O4 nanoparticles was coated with sodium dodecyl sulfate to form a nano-sized admicelle magnetic sorbent. Owing to electrostatic interaction, the alkaloids were adsorbed onto the oppositely charged admicelle magnetic nanoparticles. The quick separation of the analyte-adsorbed nanoparticles from the sample solution was performed by using Nd-Fe-B magnet. Best extraction efficiency was achieved under the following conditions: 800 μL Fe3O4 nanoparticles suspension (20 mg/mL), 150 μL sodium dodecyl sulfate solution (10 mg/mL), pH 2, and vortexing time 2 min for the extraction of alkaloids from 10 mL of diluted sample. Four hundred microliters of methanol was used to desorb the alkaloids by vortexing for 1 min. Satisfactory extraction recoveries were obtained in the range of 85.9–120.3%, relative standard deviations for intra- and interday precisions were less than 6.3 and 10.0%, respectively. Finally, the established method was successfully applied to analyze the alkaloids in two batches of Gegen-Qinlian oral liquids.



Quality assessment of Herba Leonuri based on the analysis of multiple components using normal- and reversed-phase chromatographic methods

2017-10-30T01:46:09.111455-05:00

A novel, improved, and comprehensive method for quality evaluation and discrimination of Herba Leonuri has been developed and validated based on normal- and reversed-phase chromatographic methods. To identify Herba Leonuri, normal- and reversed-phase high-performance thin-layer chromatography fingerprints were obtained by comparing the colors and Rf values of the bands, and reversed-phase high-performance liquid chromatography fingerprints were obtained by using an Agilent Poroshell 120 SB-C18 within 28 min. By similarity analysis and hierarchical clustering analysis, we show that there are similar chromatographic patterns in Herba Leonuri samples, but significant differences in counterfeits and variants. To quantify the bio-active components of Herba Leonuri, reversed-phase high-performance liquid chromatography was performed to analyze syringate, leonurine, quercetin-3-O-robiniaglycoside, hyperoside, rutin, isoquercitrin, wogonin, and genkwanin simultaneously by single standard to determine multi-components method with rutin as internal standard. Meanwhile, normal-phase high-performance liquid chromatography was performed by using an Agilent ZORBAX HILIC Plus within 6 min to determine trigonelline and stachydrine using trigonelline as internal standard. Innovatively, among these compounds, bio-active components of quercetin-3-O-robiniaglycoside and trigonelline were first determined in Herba Leonuri. In general, the method integrating multi-chromatographic analyses offered an efficient way for the standardization and identification of Herba Leonuri.



Recent progress in nucleic acids isotachophoresis

2017-10-30T01:45:49.778978-05:00

Progress achieved between 2014–2017 in the extraction and sample preparation of nucleic acid by isotachophoresis is reviewed in this paper. The isolation and purification of nucleic acids is very often compromised by a complex matrix such as blood and other bodily fluids, samples from the scene of crime, fossil samples, etc. While most of the common nucleic acids isolation techniques are based on extraction with inherent limitations with regard to quantitative results, isotachophoretic focusing is a quantitative process with a theoretically unlimited concentration factor. Since isotachophoresis belongs to less traditional approaches of nucleic acids purification, we present not only the latest developments in the application of isotachophoresis for the nucleic acids concentration but also a brief description of the principles of this method.



Multivariate optimization of dispersive liquid–liquid microextraction for the determination of paclobutrazol and triflumizole in water by GC–MS

2017-10-30T01:45:32.458149-05:00

A new analytical method based on dispersive liquid–liquid microextraction with gas chromatography mass spectrometry has been optimized for the simultaneous determination of paclobutrazol and triflumizole in tap water and wastewater samples. A two-level, full-factorial design that allowed the study of main effects and factor interactions was applied to analyze the influence on microextraction process by chloroform, ethanol, potassium iodide and hand shaking period. The extraction conditions selected were 200 μL of chloroform, 3.0 mL of ethanol, 2.0 g of potassium iodide and 15 s of hand shaking. The limits of detection obtained for triflumizole and paclobutrazol under optimum conditions were 0.97 and 0.29 ng/mL, respectively. Calibration plots of both analytes were linear over a wide concentration range, and good precision was observed for replicate measurements. Applicability and accuracy of the method were determined by performing spiked recovery tests. Appreciable recovery results were obtained for municipal wastewater and matrix matching was used to obtain close to 100% recovery for tap water.



Poly(norepinephrine)-coated open tubular column for the separation of proteins and recombination human erythropoietin by capillary electrochromatography

2017-10-30T01:41:11.613276-05:00

Recombinant human erythropoietin is an important therapeutic protein with high economic interest due to the benefits provided by its clinical use for the treatment of anemias associated with chronic renal failure and chemotherapy. In this work, a poly(norepinephrine)-coated open tubular column was successfully prepared based on the self-polymerization of norepinephrine under mild alkaline condition, the favorable film forming and easy adhesive properties of poly(norepinephrine). The poly(norepinephrine) coating was characterized by scanning electron microscopy and measurement of the electro-osmotic flow. The thickness of the coating was about 431 nm. The electrochromatographic performance of the poly(norepinephrine)-coated open tubular column was evaluated by separation of proteins. Some basic and acidic proteins including two variants of bovine serum albumin and two variants of β-lactoglobulin achieved separation in the poly(norepinephrine)-coated open tubular column. More importantly, the column demonstrated separation ability for the glycoforms of recombinant human erythropoietin. In addition, the column demonstrated good repeatability with the run-to-run, day-to-day, and column-to-column relative standard deviations of migration times of proteins less than 3.40%.



Characterization of stress degradation products of amodiaquine dihydrochloride by liquid chromatography with high-resolution mass spectrometry and prediction of their properties by using ADMET Predictor™

2017-10-30T01:41:01.167107-05:00

The degradation behavior of amodiaquine dihydrochloride, an antimalarial drug, was investigated in solution as well as solid states. The drug was subjected to hydrolytic, photolytic, oxidative, and thermal stress conditions, according to International Conference on Harmonization guideline Q1A(R2). It showed extensive hydrolysis in acidic, alkaline, and neutral solutions both with and without light, while it proved to be stable to thermal and oxidative conditions. In total, six degradation products were formed, which were separated on a C8 column, employing a gradient reversed-phase high-performance liquid chromatography method in which acetonitrile and 10 mM ammonium formate (pH 3.0) were used in the mobile phase. To characterize the degradation products, mass fragmentation behavior of the drug was established by direct infusion of solution to quadrupole time-of-flight and multiple-stage mass spectrometry systems. Liquid chromatography with high-resolution mass spectrometry studies were subsequently carried out on the stressed samples using the same gradient high-performance liquid chromatography method employed for the separation of the degradation products. Hydrogen/deuterium exchange studies were additionally conducted to determine the number of labile hydrogen atoms. The degradation pathway of the drug was delineated, justified by mechanistic explanation. Lastly, ADMET Predictor™ software was employed to predict relevant physicochemical and toxicity data for the degradation products.



Preparation of a long-alkyl-chain-based hybrid monolithic column with mixed-mode interactions using a “one-pot” process for pressurized capillary electrochromatography

2017-10-30T01:40:40.40467-05:00

A simple “one-pot” approach for the preparation of a new vinyl-functionalized organic–inorganic hybrid monolithic column is described. In this improved method, the hydrolyzed alkoxysilanes of tetramethoxysilane and triethoxyvinylsilane were used as precursors for the synthesis of a silica-based monolith, while 1-hexadecene and sodium ethylenesulfonate were used as vinyl functional monomers along with azobisisobutyronitrile as an initiator. The effects of reaction temperature, urea content, and composition of organic monomers on the column properties (e.g. morphology, mechanical stability, and chromatographic performance) were investigated. The monolithic column was used for the separation of neutral solutes by reversed-phase pressurized capillary. Furthermore, the monolith can separate various aromatic amines, which indicated its excellent cation-exchange capability and hydrophobic interactions. The baseline separation of the aromatic amines was obtained with a column efficiency of up to 78 000 plates/m.



Evaluation of the quality consistency of powdered poppy capsule extractive by an averagely linear-quantified fingerprint method in combination with antioxidant activities and two compounds analyses

2017-10-27T12:51:19.352569-05:00

A novel averagely linear-quantified fingerprint method was proposed and successfully applied to monitor the quality consistency of alkaloids in powdered poppy capsule extractive. Averagely linear-quantified fingerprint method provided accurate qualitative and quantitative similarities for chromatographic fingerprints of Chinese herbal medicines. The stability and operability of the averagely linear-quantified fingerprint method were verified by the parameter r. The average linear qualitative similarity SL (improved based on conventional qualitative “Similarity”) was used as a qualitative criterion in the averagely linear-quantified fingerprint method, and the average linear quantitative similarity PL was introduced as a quantitative one. PL was able to identify the difference in the content of all the chemical components. In addition, PL was found to be highly correlated to the contents of two alkaloid compounds (morphine and codeine). A simple flow injection analysis was developed for the determination of antioxidant capacity in Chinese Herbal Medicines, which was based on the scavenging of 2,2-diphenyl-1-picrylhydrazyl radical by antioxidants. The fingerprint–efficacy relationship linking chromatographic fingerprints and antioxidant activities was investigated utilizing orthogonal projection to latent structures method, which provided important pharmacodynamic information for Chinese herbal medicines quality control. In summary, quantitative fingerprinting based on a[...]



A validated LC–MS/MS method for the simultaneous determination of 20-(S)-protopanaxatriol and its two active metabolites in rat plasma: Application to a pharmacokinetics study

2017-10-27T12:50:59.708605-05:00

We present a validated liquid chromatography with tandem mass spectrometry method for simultaneous determination of 20-(S)-protopanaxatriol and its two oxidative stereoisomeric metabolites (20S,24S)-epoxy-dammarane-3,6,12,25-tetraol (M1) and (20S,24R)-epoxy-dammarane-3,6,12,25-tetraol (M2) in rat plasma. 20-(S)-Protopanaxatriol, M1, and M2 were extracted with methanol and separated on an ACQUITY HSS T3 column. The mass spectrometry detection was accomplished in selected reaction monitoring mode with precursor-to-product ion transitions of m/z 493.4143.1 for M1 and M2, m/z 475.4391.3 for 20-(S)-protopanaxatriol, and m/z 459.4375.3 for 20-(S)-protopanaxadiol (internal standard). The method showed good linearity over the concentration ranges of 1–1000 ng/mL for 20-(S)-protopanaxatriol and 0.5–200 ng/mL for M1 and M2, with correlation coefficients of more than 0.995. The lower limits of quantification for 20-(S)-protopanaxatriol, M1, and M2 were 1, 0.5, 0.5 ng/mL, respectively. The intra- and interday precisions (RSD, %) were less than 10.41% while the accuracy (relative error, %) ranged from –3.14 to 8.73%. Under the current conditions, M1 and M2 were completely separated within 3 min. The validated assay was successfully applied to evaluating pharmacokinetic profiles of 20-(S)-protopanaxatriol, M1, and M2 in rat.



Ionic liquids: solvents and sorbents in sample preparation

2017-10-17T00:25:49.057065-05:00

The applications of ionic liquids (ILs) and IL-derived sorbents are rapidly expanding. By careful selection of the cation and anion components, the physicochemical properties of ILs can be altered to meet the requirements of specific applications. Reports of IL solvents possessing high selectivity for specific analytes are numerous and continue to motivate the development of new IL-based sample preparation methods that are faster, more selective, and environmentally benign compared to conventional organic solvents. The advantages of ILs have also been exploited in solid/polymer formats in which ordinarily nonspecific sorbents are functionalized with IL moieties in order to impart selectivity for an analyte or analyte class. Furthermore, new ILs that incorporate a paramagnetic component into the IL structure, known as magnetic ionic liquids (MILs), have emerged as useful solvents for bioanalytical applications. In this rapidly changing field, this Review focuses on the applications of ILs and IL-based sorbents in sample preparation with a special emphasis on liquid phase extraction techniques using ILs and MILs, IL-based solid-phase extraction, ILs in mass spectrometry, and biological applications.



Modeling and predicting the solute polarity parameter in reversed-phase liquid chromatography using quantitative structure–property relationship approaches

2017-10-12T01:20:52.095465-05:00

A prediction of quantitative structure–property relationships is developed to model the polarity parameter of a set of 146 organic compounds in acetonitrile in reversed-phase liquid chromatography. Enhanced replacement method and support vector machine regressions were employed to build prediction models based on molecular descriptors calculated from the structure alone. The correlation coefficients between experimental and predicted values of polarity parameter for the test set by enhanced replacement method and support vector machine were 0.970 and 0.993, respectively. The obtained results demonstrated that the support vector machine model is more reliable and has a better prediction performance than the enhanced replacement method.



Monitoring of transferrin isoforms in biological samples by capillary electrophoresis

2017-10-10T04:40:37.939773-05:00

Work dealing with the monitoring of transferrin isoforms in human serum and other body fluids by capillary electrophoresis is reviewed. It comprises capillary zone electrophoresis and capillary isoelectric focusing efforts that led to the exploration and use of assays for the determination of carbohydrate-deficient transferrin as a marker for excessive alcohol intake, genetic variants of transferrin, congenital disorders of glycosylation and β-2-transferrin, which is a marker for cerebrospinal fluid leakage. This paper provides insight into the development, specifications, strengths, weaknesses, and routine use of the currently known capillary electrophoresis based assays suitable to detect transferrin isoforms in body fluids. The achievements reached so far indicate that capillary zone electrophoresis is an attractive technology to monitor the molecular forms of transferrin in biological specimens as the assays do not require an elaborate sample pretreatment and thus can be fully automated for high-throughput analyses on multicapillary instruments. Assays based on capillary isoelectric focusing are less attractive. They require immunoextraction of transferrin from the biological matrix and mobilization after focusing if instrumentation with a whole-column imaging detector is not available. Interactions of the carrier ampholytes with the iron of transferrin may preve[...]