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Journal of Separation Science



Wiley Online Library : Journal of Separation Science



Published: 2017-09-01T00:00:00-05:00

 



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

2017-09-23T06:20:52.753056-05:00

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 enhanced replacement method. This article is protected by copyright. All rights reserved



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

2017-09-23T02:50:22.238137-05:00

A new analytical method based on dispersive liquid–liquid microextraction with gas chromatography and 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. 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−1, 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. This article is protected by copyright. All rights reserved



Evaluation of two membrane-based microextraction techniques for the determination of endocrine disruptors in aqueous samples by HPLC with diode array detection

2017-09-23T01:50:22.048374-05:00

In this study, the viability of two membrane-based microextraction techniques for the determination of endocrine disruptors by high-performance liquid chromatography with diode array detection was evaluated: hollow fiber microporous membrane liquid–liquid extraction and hollow-fiber-supported dispersive liquid–liquid microextraction. The extraction efficiencies obtained for methylparaben, ethylparaben, bisphenol A, benzophenone and 2-ethylhexyl-4-methoxycinnamate from aqueous matrices obtained using both approaches were compared and showed that hollow fiber microporous membrane liquid–liquid extraction exhibited higher extraction efficiency for most of the compounds studied. Therefore, a detailed optimization of the extraction procedure was carried out with this technique. The optimization of the extraction conditions and liquid desorption were performed by univariate analysis. The optimal conditions for the method were supported liquid membrane with 1-octanol for 10 s, sample pH 7, addition of 15% w/v of NaCl, extraction time of 30 min and liquid desorption in 150 μL of acetonitrile/methanol (50:50 v/v) for 5 min. The linear correlation coefficients were higher than 0.9936. The limits of detection were 0.5–4.6 μg L−1 and the limits of quantification were 2–16 μg L−1. The analyte relative recoveries were 67–116%, and the relative standard deviations were less than 15.5%. This article is protected by copyright. All rights reserved



Bioactive compounds of Shuang-Huang-Lian prescription and an insight into its binding mechanism by β2-adrenoceptor chromatography coupled with site-directed molecular docking

2017-09-20T03:50:21.82212-05:00

Owing to the promising clinical efficacy and relatively simple composition, Shuang-Huang-Lian prescription is widely prescribed for the treatment of acute upper respiratory tract infection and acute bronchitis in practice. This necessitates the understanding of the bioactive compounds of the prescription and their binding mechanism to β2-adrenoceptor, which mediates the aforementioned ailments. In this work, a column containing immobilized β2-adrenoceptor was prepared using a diazonium salt reaction. The bioactive compound collected from the β2-adrenoceptor column was identified as chlorogenic acid by using high-performance liquid chromatography coupled with ion trap mass spectrometry. Using an injection amount dependent method, chlorogenic acid proved the binding to β2-adrenoceptor through two kinds of sites. The numbers of the sites were (1.42±0.03) × 10−8 and (9.06±0.49) × 10−8 M. The association constants were (2.72±0.01) × 105 and (2.80±0.01) × 104 M−1, respectively. Molecular docking analysis of the interaction between chlorogenic acid and β2-adrenoceptor indicated that the binding mainly occurred on Ser169, Ser173 and Phe287 of β2-adrenoceptor. These results paved the way to screen bioactive compounds of other traditional medicines by receptor chromatography. This article is protected by copyright. All rights reserved



Precise control of agarose media pore structure by regulating cooling rate

2017-09-19T21:50:31.562047-05:00

A porous structure is the key factor to successful chromatography separation. Agarose gel as one of the most popular porous media has been extensively used in chromatography separation. As the cooling process in the agarose gelation procedure can directly influence the pore structure, ten kinds of 4% agarose media with different cooling rates from 0.132 to 16.7°C/min were synthesized, and the pore structure was determined accurately by using low-field NMR spectroscopy. The curves of pore structure and cooling rate can be divided into two stages with the boundary of 6°C/min. In stage I, the pore structure met a power equation with the decrease of the cooling rate, and in stage II, the process reached a plateau. Confirmatory experiments proved that, by adjusting the cooling rate, a precise control of the pore structure of agarose media can be realized, furthermore, cooling rate optimization was an effective way to control the pore size of agarose media and can further tailor the pore structure for more effective separation of different proteins. This article is protected by copyright. All rights reserved



Development of a simple and valid method for the trace determination of phthalate esters in human plasma using dispersive liquid–liquid microextraction coupled with GC–MS

2017-09-19T11:20:20.237642-05:00

A new method was developed for the trace determination of phthalic acid esters in plasma using dispersive liquid–liquid microextraction and gas chromatography with mass spectrometry analysis. Plasma proteins were efficiently precipitated by trichloroacetic acid and then a mixture of chlorobenzene (as extraction solvent) and acetonitrile (as dispersive solvent) rapidly injected to clear supernatant using a syringe. After the centrifuging, chlorobenzene were sedimented in the bottom of the test tube. 1 μL of this sedimented phase was injected into the gas chromatograph for phthalic acid esters analysis. Different factors affecting the extraction performance, such as the type of extraction and dispersive solvent, their volume, extraction time and the effects of salt addition were investigated and optimized. Under the optimum conditions, the enrichment factors and extraction recoveries were satisfactory and ranged between 820–1020 and 91–97%, respectively. The linear range was wide (50–1000 ng mL−1) and limit of detection was very low (1.5–2.5 ng mL−1 for all analytes). The relative standard deviations for analysis of 1 μg mL−1 of the analytes were between 3.2–6.1%. Salt addition showed no significant effect on extraction recovery. Finally, the proposed method was successfully utilized for the extraction and determination of the phthalic acid esters in human plasma samples and satisfactory results were obtained. This article is protected by copyright. All rights reserved



Qualitative and quantitative analysis of chemical constituents in Ardisiae Japonicae Herba

2017-09-19T09:20:20.435494-05:00

Ardisiae Japonicae Herba is a well-known traditional Chinese medicine for the treatment of bronchitis conjunctivitis, pneumonia and trauma. In this work, a high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was firstly established for the separation and structural identification of the chemical constituents in Ardisiae Japonicae Herba. A total of 15 compounds including coumarins, flavonoid glycosides, and catechins were identified or tentatively characterized based on their chromatographic behaviors and mass spectral fragmentation and by comparisons with the reference standards. Furthermore, a simple high-performance liquid chromatography with diode array detection method was developed to for the simultaneous determination of five major constituents. Results obtained from method validations including linearity, precision, repeatability, stability and recovery showed that the established method was reliable and accurate. Bergenin and quercitrin were found to be the most abundant constituents and could be served as chemical markers for quality control of Ardisiae Japonicae Herba. This article is protected by copyright. All rights reserved



Ionic Liquids: Solvents and Sorbents in Sample Preparation

2017-09-19T08:51:04.10474-05:00

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 non-specific 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. This article is protected by copyright. All rights reserved



Non-targeted volatile profiles for the classification of the botanical origin of Chinese honey by solid-phase microextraction and GC–MS combined with chemometrics

2017-09-19T07:50:41.703911-05:00

A potential method for the discrimination and prediction of honey samples of various botanical origins was developed based on the non-targeted volatile profiles obtained by solid-phase microextraction with gas chromatography and mass spectrometry combined with chemometrics. The blind analysis of non-targeted volatile profiles was carried out using solid-phase microextraction with gas chromatography and mass spectrometry for 87 authentic honey samples from four botanical origins (acacia, linden, vitex and rape). The number of variables was reduced from 2734 to 70 by using a series of filters. Based on the optimized 70 variables, 79.12% of the variance was explained by the first four principal components. Partial least squares discriminant analysis, naïve Bayes analysis and back-propagation artificial neural network were used to develop the classification and prediction models. The 100% accuracy revealed a perfect classification of the botanical origins. In addition, the reliability and practicability of the models were validated by an independent set of an additional 20 authentic honey samples. All 20 samples were accurately classified. The confidence measures indicated that the performance of the naïve Bayes model was better than the other two models. Finally, the characteristic volatile compounds of linden honey were tentatively identified. The proposed method is reliable and accurate for the classification of honey of various botanical origins. This article is protected by copyright. All rights reserved



Strategies for analysis of isomeric peptides

2017-09-18T09:50:44.094426-05:00

This review presents an overview and recent progress of strategies for detecting isomerism in peptides, with focus on d/l epimerization and the various isomers that the presence of an aspartic acid residue may yield in a protein or peptide. While mass spectrometry has become a majorly used method of choice within proteomics, isomerism is inherently difficult to analyze because it is a modification that does not yield any change in mass of the analyte. Here, several techniques used for analysis of peptide isomerism are discussed, including enzymatic assays, liquid chromatography and capillary electrophoresis. Recent progress in method development using mass spectrometry is also discussed, including labeling strategies, fragmentation techniques, and ion-mobility spectrometry. This article is protected by copyright. All rights reserved



Performance comparison of dispersive solid-phase extraction and multiplug filtration cleanup methods for the determination of tefuryltrione in plant and environmental samples using UHPLC–MS/MS

2017-09-18T07:22:07.659862-05:00

The detection frequencies of tefuryltrione, a new type of 4-hydroxyphenyl-pyruvate dioxygenase inhibitor herbicide, are rarely reported, probably because of the paucity of analytical methods. Herein, an effective and sensitive analytical method has been developed to detect tefuryltrione in vegetables (tomato and cucumber), cereals (rice and corn), soil and water by ultra high performance liquid chromatography coupled with tandem mass spectrometry. Comparisons of the performances of dispersive solid-phase extraction and multiplug filtration cleanup methods were carried out for tefuryltrione in complex matrices. Extraction solvents and purification sorbents were further optimized for dispersive solid-phase extraction. Tefuryltrione was analyzed with electrospray ionization in the positive mode (ESI+) within 2.0 min. Mean recoveries for tefuryltrione were 75.4–108.9% with relative standard deviations less than 11.0% at three fortification levels (10, 100, 500 μg/kg) in the sample matrixes. Limits of quantification ranged from 0.70 to 5.12 μg/kg, and an excellent linearity (R2 ≥ 0.9902) was obtained for tefuryltrione at concentrations of 5–1000 μg/L. The results showed that the developed dispersive solid-phase extraction method could serve as an effective, sensitive and robust method for routine monitoring of tefuryltrione residue in plants and environmental samples. This article is protected by copyright. All rights reserved



Synthesis of monodisperse silica microspheres and modification with diazoresin for mixed-mode ultra high performance liquid chromatography separations

2017-09-13T08:21:57.198864-05:00

Monodisperse silica particles with average diameters of 1.9–2.9 μm were synthesized by a modified Stöber method, in which tetraethyl orthosilicate was continuously supplied to the reaction mixture containing KCl electrolyte, water, ethanol and ammonia. The obtained silica particles were modified by self-assembly with positively charged photosensitive diazoresin on the surface. After treatment with ultraviolet light, the ionic bonding between silica and diazoresin was converted into covalent bonding through a unique photochemistry reaction of diazoresin. Depending on the chemical structure of diazoresin and mobile phase composition, the diazoresin-modified silica stationary phase showed different separation mechanisms, including reversed phase and hydrophilic interactions. Therefore, a variety of baseline separation of benzene analogues and organic acids was achieved by using the diazoresin modified silica particles as packing materials in ultra high performance liquid chromatography. According to the π–π interactional difference between carbon rings of fullerenes and benzene rings of diazoresin, C60 and C70 were also well separated by ultra high performance liquid chromatography. Because it has a small size, the ∼2.5 μm monodisperse diazoresin-modified silica stationary phase shows ultra high efficiency compared with the commercial C18-silica high-performance liquid chromatography stationary phase with average diameters of ∼5 μm. This article is protected by copyright. All rights reserved



Optimization of the ultrasound-assisted extraction of antioxidant phloridzin from Lithocarpus polystachyus Rehd. using response surface methodology

2017-09-12T07:50:37.988727-05:00

The purpose of this study was to optimize the extraction process of phloridzin from Lithocarpus polystachyus Rehd. leaves using response surface methodology and to determine the antioxidant capacity of the extract. A Box–Behnken design was used to analyze the effects of ethanol concentration, liquid–solid ratio, soak time and extraction time on the extraction yield of phloridzin. The content of phloridzin was determined by high-performance liquid chromatography. To assess the antioxidant capacity of the extract, three in vitro test systems were used (1,1-,diphenyl-2-picrylhydrazyl, hydroxyl radical scavenging test and reduction force). The optimal parameters obtained by response surface methodology were a volume fraction of ethanol of 64%, a liquid–solid ratio of 37:1, a soaking time of 35 h and a sonication time of 38 min. The proportion of the extraction of phloridzin from L. polystachyus under these industrial process conditions was 3.83%. According to the obtained results, response surface methodology could be suggested as an adequate model for optimizing the extraction process of phloridzin from L. polystachyus. Ultrasound extraction significantly increased the extraction rate of phloridzin, which could be used as an antioxidant in pharmaceutical and food products. This article is protected by copyright. All rights reserved



Direct preparation of a graphene oxide modified monolith in a glass syringe as a solid-phase extraction cartridge for the extraction of quaternary ammonium alkaloids from Chinese patent medicine

2017-09-12T07:21:38.538774-05:00

Packed cartridges have been widely used in solid-phase extraction. However, there are still some drawbacks, such as they are blocked easily and the method is time-consuming. In view of the advantages of monoliths, a monolithic extraction material has been directly synthesized in a glass syringe without any gap between the monolith and syringe's inner wall. The monolithic syringe was modified with graphene oxide by loading a graphene oxide dispersion onto it. The content of graphene oxide and the surface topography of the monolith have been evaluated by elemental analysis and scanning electron microscopy, respectively, which confirmed the successful modification. This prepared graphene oxide modified monolithic syringe was directly used as a traditional solid-phase extraction cartridge. As expected, it shows good permeability and excellent capability for the extraction of quaternary ammonium alkaloids. The sample loading velocity (1–6 mL·min−1) does not affect the recovery. Under the optimal conditions, good linearities (R = 0.9992–0.9998) were obtained for five quaternary ammonium alkaloids, and the limits of detection and quantification were 0.5-1 and 1–2 μg·L−1, respectively. The proposed method was successfully applied for the analysis of quaternary ammonium alkaloids in Chinese patent medicine. This article is protected by copyright. All rights reserved



Purification of polysaccharide from artificially cultivated Anoectochilus roxburghii(wall.) Lindl. by high-speed counter current chromatography and its antitumor activity

2017-09-11T10:04:43.909305-05:00

To establish a systematic method for the extraction, purification, characterization and antitumor activity study of polysaccharide from artificially cultivated Anoectochilus roxburghii(wall.) Lindl. (AC-ARPS). High-speed counter current chromatography with two-phase aqueous systems was successfully applied to purify AC-ARPS after one-step separation. The purity of the AC-ARPS obtained by phenol/sulfuric acid method was 95.01%. The chemical structures of AC-ARPS were identified by a series analytical methods including high-performance liquid chromatography and liquid chromatography with mass spectrometry. High-performance liquid chromatography and liquid chromatography with mass spectrometry indicated that AC-ARPS was mainly composed of mannose, ribose, glucose, galactose and arabinose with a molar ratio of 1.00:8.47:47.30:1.17:1.19. AC-ARPS is a homogeneous polysaccharide with a molecular weight of 25 681 Da. The antitumor effect of AC-ARPS was evaluated on lung cancer A549, osteosarcoma 143B, rat adrenal pheochromocytoma PC 12, breast cancer MCF-7, acute leukemia HL 60, chronic leukemia K562, colon cancer SW620, esophageal cancer OE 19, liver cancer HepG2, and neuroglioma U251 cells in vitro. AC-ARPS showed the best inhibitory effect on OE 19 cells, and the IC50 value was 5.67 ± 0.831 μmol/L. Fluorescence analysis and flow cytometry results showed that AC-ARPS induced apoptosis and G2/M phase arrest in OE 19 cells. This article is protected by copyright. All rights reserved



Molecular characterization of branched polysaccharides from Tremella fuciformis by asymmetrical flow field-flow fractionation and size exclusion chromatography

2017-09-11T02:20:26.514037-05:00

To accurately characterize branched polysaccharides with high molecular weights from medicinal and edible mushrooms and identify the limitations of size exclusion chromatography, molecular characteristics of polysaccharides from Tremella fuciformis were determined and compared by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering and refractive index detection, and size exclusion chromatography coupled with multi-angle laser light scattering and refractive index detection, respectively. Results showed that molecular weights of three batches of T. fuciformis polysaccharides were determined as 2.167 × 106 (TF1), 2.334 × 106 (TF2), and 2.435 × 106 Da (TF3) by size exclusion chromatography, and 3.432 × 106 (TF1), 3.739 × 106 (TF2), and 3.742 × 106 Da (TF3) by asymmetrical flow field-flow fractionation, as well as 3.469 × 106 Da (TF1) by off-line multi-angle laser light scattering, respectively. Results suggested that size exclusion chromatography was unable to accurately characterize T. fuciformis polysaccharides, which may due to its limitations such as shear degradation and abnormal co-elution. Compared to size exclusion chromatography, asymmetrical flow field-flow fractionation could be a better technique for the molecular characterization of branched polysaccharides with high molecular weights from medicinal and edible mushrooms, as well as from other natural resources. This article is protected by copyright. All rights reserved



Comparison of four extraction methods for analysis of volatile hop-derived aroma compounds in beer

2017-09-09T02:20:28.202006-05:00

The volatile organic compound profile in beer is derived from hops, malt, yeast, and interactions between the ingredients, making it very diverse and complex. Due to the range and diversity of the volatile organic compounds present, the choice of the extraction method is extremely important for optimal sensitivity and selectivity. This study compared four extraction methods for hop-derived compounds in beer late hopped with Nelson Sauvin. Extraction capacity and variation were compared for headspace solid phase micro extraction, stir bar sorptive extraction, headspace sorptive extraction, and solvent assisted flavour evaporation. Generally, stir bar sorptive extraction was better suited for acids, headspace sorptive extraction for esters and aldehydes, while headspace solid phase micro extraction was less sensitive overall, extracting 40% fewer compounds. Solvent assisted flavour evaporation with dichloromethane was not suitable for the extraction of hop-derived volatile organic compounds in beer, as the profile was strongly skewed towards alcohols and acids. Overall, headspace sorptive extraction found to be best suited, closely followed by stir bar sorptive extraction. This article is protected by copyright. All rights reserved



Monitoring of transferrin isoforms in biological samples by capillary electrophoresis

2017-09-08T08:50:35.30925-05:00

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 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 for monitoring of 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 prevent iron saturation and thus provide more complicated isoform patterns. This article is protected by copyright. All rights reserved



Osteoblast cell membrane chromatography coupled with liquid chromatography and time-of-flight mass spectrometry for screening specific active components from traditional Chinese medicines

2017-09-08T06:21:50.200611-05:00

A method using osteoblast membrane chromatography coupled with liquid chromatography and time-of-flight mass spectrometry was developed to recognize and identify the specific active components from traditional Chinese medicines. Primary rat osteoblasts were used for the preparation of the stationary phase in the cell chromatography method. Retention components from the cell chromatography were collected and analyzed by liquid chromatography with time-of-flight mass spectrometry. This method was applied in screening active components from extracts of four traditional Chinese medicines. In total, 24 potentially active components with different structures were retained by osteoblast cell chromatography. There were five phenolic glucosides and one triterpenoid saponin from Curculigo orchioides Gaertn, two organic acids and ten flavonoids from Epimedium sagittatum Maxim, one phthalide compound and one organic acid from Angelica sinensis Diels, and two flavonoids and two saponins from Anemarrhena asphodeloides Bunge. Among those, four components (icariin, curculigoside, ferulaic acid, and timosaponin BII) were used for in vitro pharmacodynamics validation. They significantly increased the osteoblast proliferation, alkaline phosphatase activity, levels of bone gla protein and collagen type 1, and promoted mineralized nodule formation. The developed method was an effective screening method for finding active components from complex medicines that act on bone diseases. This article is protected by copyright. All rights reserved



Hydrophilic interaction liquid chromatography tandem mass spectrometry analysis of malonyl-coenzyme A in breast cancer cell cultures applying online solid-phase extraction

2017-09-06T12:50:23.105049-05:00

Cofactors such as coenzyme A and its derivatives acetyl-coenzyme A and malonyl-coenzyme A are involved in many metabolic pathways. Due to trace level concentrations in biological samples and the high reactivity of cofactors, a fast, sensitive and selective method for quantification is mandatory. In this study, online solid-phase extraction was coupled successfully to hydrophilic interaction liquid chromatography with tandem mass spectrometry for analytes’ isolation in complex matrix and quantification by external calibration. Online solid-phase extraction was carried out by application of a weak anion exchange column, whereas hydrophilic interaction liquid chromatography separation was performed on an amide modified stationary phase. Sample preparation of the extracts prior the analysis was reduced to a centrifugation and dilution step. Moreover, the applied online solid-phase extraction significantly reduced matrix effects and increased the signal-to-noise ratio. The limit of detection and the limit of quantification were in the lower nanomolar range. Finally, the applicability of this method was demonstrated on MCF-7 breast cancer cell cultures, a common used model system, where acetyl-coenzyme A and malonyl-coenzyme A were determined with standard addition procedure in concentrations of 1.98 μM and 41 nM, respectively. This article is protected by copyright. All rights reserved



Application of dispersive liquid–liquid microextraction for the preconcentration of eight parabens in real samples and their determination by HPLC

2017-09-06T12:21:25.364506-05:00

A simple and sensitive method for the simultaneous determination of eight parabens in human plasma and urine samples was developed. The samples were preconcentrated using dispersive liquid–liquid microextraction based on the solidification of floating organic drops and determined by high-performance liquid chromatography with UV detection. The influence of variables affecting the extraction efficiency was investigated and optimized using Placket–Burman design and Box–Behnken design. The optimized values were: 58 μL of 1-decanol (as extraction solvent), 0.65 mL methanol (as disperser solvent), 1.5% w/v NaCl in 5.0 mL of sample solution, pH 10.6, and 4.0 min centrifugation at 4000 rpm. The extract was injected into the high-performance liquid chromatography system for analysis. Under the optimum conditions, the linear ranges for eight parabens in plasma and urine were 1.0–1000 ng/mL, with correlation coefficients above 0.994. The limit of detection was 0.2–0.4 and 0.1–0.4 ng/mL for plasma and urine samples, respectively. Relative recoveries were between 80.3 and 110.7%, while relative standard deviations were less than 5.4%. Finally, the method was applied to analysis the parabens in 98 patients of primary breast cancer. Results showed that parabens existed widely, at least one paraben detected in 96.9% (95/98) of plasma samples and 98.0% (96/98) of urine samples. This article is protected by copyright. All rights reserved



Recent progress of task-specific ionic liquids in chiral resolution and extraction of biological samples and metal ions

2017-09-06T10:33:44.347302-05:00

Ionic liquids have been functionalized for modern applications. The functional ionic liquids are also called task-specific ionic liquids. Various task-specific ionic liquids with certain groups have been constructed and exploited widely in the field of separation. To take advantage of their properties in separation science, task-specific ionic liquids are generally used in techniques such as liquid–liquid extraction, solid-phase extraction, gas chromatography, high-performance liquid chromatography and capillary electrophoresis. This review mainly covers original research papers published in the last five years, and we will focus on task-specific ionic liquids as the chiral selectors in chiral resolution and as extractant or sensor for biological samples and metal ion purification. This article is protected by copyright. All rights reserved



HPLC thermodynamic study of new potential antiepileptic compounds on cholesterol column using isocratic elution with methanol/water and acetonitrile/water eluent systems

2017-09-04T14:20:45.15181-05:00

Basic thermodynamic functions responsible for retention of new 1,2,4-triazole derivatives exhibiting varied antiepileptic activity on cholesterol-based stationary phase were determined. Evaluation of the Gibbs energy change, the change in enthalpy and the change in entropy was based on the van ’t Hoff relationship representing ln k vs. 1/T. A detailed discussion of the van ’t Hoff equation, exploring the influence of the phase ratio on deviations from linearity in a Van ’t Hoff plot is presented. We show chromatographic evidence to the question of how a varied mobile phase composition may cause different thermodynamic phase ratios. The analysis of data from a differential scanning calorimetry excluded any phase transitions of either the individual solutes or cholesterol stationary phase suspended in the mobile phase components within the studied temperature range. This article is protected by copyright. All rights reserved



Development of multiple monolithic fiber solid-phase microextraction and LC–MS/MS method for the sensitive monitoring of aminoglycosides in honey and milk samples

2017-09-04T05:25:02.353789-05:00

A simple and sensitive method for the simultaneous extraction and determination of six aminoglycosides in honey and milk samples has been developed using multiple monolithic fiber solid-phase microextraction and liquid chromatography with tandem mass spectrometry. The multiple monolithic fibers based on poly (methacrylic acid-co-ethylenedimethacrylate) monolith as extractive medium was used to concentrate target analytes. Because there were abundant carboxyl groups in the monolith, the monolithic fibers could extract aminoglycosides effectively through cation-exchange and hydrophobic interactions. To obtain optimum extraction performance, several extraction parameters including desorption solvent, adsorption and desorption time, pH value and ionic strength in sample matrix, were investigated in detail. Under the optimized extraction conditions, the limits of detection of the proposed method were 0.10–0.30 and 0.23–0.59 μg/kg for honey and milk samples, respectively. Satisfactory linearity was achieved for analytes with the coefficients of determination above 0.99. At the same time, the developed method showed acceptable method repeatability and reproducibility. Finally, the proposed method was successfully applied to the determination of aminoglycosides in real honey and milk samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 67.9 to 110%, and the relative standard deviations were in the range of 1.2–11%. This article is protected by copyright. All rights reserved



Rapid separation and simultaneous quantitative determination of 13 constituents in Psoraleae Fructus by a single marker using HPLC with diode array detection

2017-09-04T04:51:16.617304-05:00

Psoraleae Fructus is one of the most popular traditional Chinese medicines. Coumarins, flavonoid and meroterpenes are the main contributors to the biological activity of Psoraleae Fructus. In this study, a new method for the quality control of Psoraleae Fructus was developed, through the quantitative analysis of multi-components by single marker with diode array detector. Thirteen components, including psoralenoside, isopsoralenoside, psoralen, isopsoralen, psoralidin, neobavaisoflavone, bavachin, corylin, isobavachalcone, corylifol A, bavachinin, bavachalcone and bakuchiol were rapidly separated and identified within 12 min by the newly developed method. The feasibility and reliability of this method were corroborated. The method was also compared to the external standard method and detection by corona charged aerosol detector. The results of percent difference (%) and cos (θ) shown that there were no significant differences observed between the quantitative analysis of multi-components by single marker and external standard method analyses, psoralen and isopsoralen were undetectable with the corona charged aerosol detector due to their volatility, but the sensitivity for all the compounds except bakuchiol detected by corona charged aerosol detector are higher than those obtained by diode array detector. In addition, the newly method developed was applied to the quality evaluation of Chinese patent medicines containing Psoraleae Fructus. This article is protected by copyright. All rights reserved



Techniques for the analysis of pentacyclic triterpenoids in medicinal plants

2017-09-01T10:50:39.68571-05:00

Triterpenes are a major class of chemical compounds found in natural plants and can be categorized into acyclic triterpenoids, monocyclic triterpenoids, tricyclic triterpenoids, tetracyclic triterpenoids, and pentacyclic triterpenoids. Among them, pentacyclic triterpenoids have gained more extensive attention due to their biological activities, including anti-inflammation, antibacterial, antioxidation, antitumor, anti-HIV, hepatoprotection, and immunological adjuvant properties. In this review we summarize the extraction and analytical methods for pentacyclic triterpenoids, where more than 56 triterpenes from 49 kinds of plants were involved. The analysis methods include gas chromatography, liquid chromatography, capillary electrophoresis, thin-layer chromatography, supercritical fluid chromatography, NMR spectroscopy and X-ray spectroscopy. This review provides valuable reference for the determination of pentacyclic triterpenoids in medicinal plants. This article is protected by copyright. All rights reserved



Mass-Spectrometry-Based Lipidomics

2017-08-31T16:00:45.134879-05:00

Lipids, which have core functions in energy storage, signalling and biofilm structures, play important roles in a variety of cellular processes because of the great diversity of their structural and physiochemical properties. Lipidomics is the large-scale profiling and quantification of biogenic lipid molecules, the comprehensive study of their pathways and the interpretation of their physiological significance based on analytical chemistry and statistical analysis. Lipidomics will not only provide insight into the physiological functions of lipid molecules but will also provide an approach to discovering important biomarkers for diagnosis or treatment of human diseases. Mass-spectrometry-based analytical techniques are currently the most widely used and most effective tools for lipid profiling and quantification. In this review, the field of mass-spectrometry-based lipidomics was discussed. Recent progress in all essential steps in lipidomics was carefully discussed in this review, including lipid extraction strategies, separation techniques, and mass-spectrometry-based analytical and quantitative methods in lipidomics. We also focused on novel resolution strategies for difficult problems in determining C = C bond positions in lipidomics. Finally, new technologies that were developed in recent years including single-cell lipidomics, flux-based lipidomics and multiomics technologies were also reviewed. This article is protected by copyright. All rights reserved



The effect of solvation processes on amino acid- and peptide-silica stationary phases

2017-08-31T13:20:31.114367-05:00

The surface excess adsorption isotherms of water, acetonitrile, and methanol from binary hydro-organic mobile phases were investigated on nine home-made stationary phases with chemically bonded amino acids, dipeptides, and tripeptides using the dynamic minor disturbance method. The stationary phases were modified by the following amino acids: glycine, alanine, phenylalanine, leucine, and aspartic acid. It allows investigating the influence of the type of immobilized amino acids, in particular their different side chains, on the solvent adsorption. The interpretation of solvation phenomena shows significant accumulation of investigated solvents on the adsorbent surface according to their hydrophilic or hydrophobic properties. Moreover, the accumulated amount was dependent on the length and type of amino acid sequences bonded to the silica surface. Stationary phases with bonded amino acids and peptides show stronger water and acetonitrile adsorption in contrast to the stationary phase modified with aminopropyl groups—a support for the synthesis. The comparison of water and acetonitrile adsorption as well as a data obtained with the two-site adsorption model reveal and confirm the heterogeneity of chemically bonded phases. As a consequence of performed investigations, the classification of tested stationary phases for the potential usage in particular high-performance liquid chromatography mode was also accomplished. This article is protected by copyright. All rights reserved



Screening, separation, and evaluation of xanthine oxidase inhibitors from Paeonia lactiflora using chromatography combined with a multi-mode microplate reader

2017-08-30T09:20:48.474275-05:00

Natural products have become one of the most important resources for discovering novel xanthine oxidase inhibitors, which are commonly employed in the treatment of hyperuricemia and gout. However, to date, few reports exist regarding the use of monoterpene glycosides as xanthine oxidase inhibitors. Thus, we herein report the use of ultrafiltration coupled with liquid chromatography in the screening of monoterpene glycoside xanthine oxidase inhibitors from the extract of Paeonia lactiflora (P. lactiflora), and both high-performance counter-current chromatography and medium-pressure liquid chromatography were employed to separate the main constituents. Furthermore, the xanthine oxidase inhibitory activities and the mechanisms of inhibition of the isolated compounds were evaluated using a multi-mode microplate reader by Molecular Devices. As a result, three monoterpene glycosides were separated by combined high-performance counter-current chromatography and medium-pressure liquid chromatography in purities of 90.4, 98.0, and 86.3%, as determined by liquid chromatography. These three compounds were identified as albiflorin, paeoniflorin, and 1-O-β-ᴅ-glucopyranosyl-8-O-benzoylpaeonisuffrone by electrospray ionization tandem mass spectrometry, and albiflorin and paeoniflorin were screened as potential xanthine oxidase inhibitors by ultrafiltration with liquid chromatography. The evaluation results of xanthine oxidase inhibitory activity corresponded with the screening results, as only albiflorin and paeoniflorin exhibited xanthine oxidase inhibitory activity. This article is protected by copyright. All rights reserved



Simultaneous determination of alcohols including diols and triols by HPLC with ultraviolet detection based on the formation of a copper(II) complex

2017-08-29T09:10:32.952454-05:00

We developed a reversed-phase high-performance liquid chromatography method with ultraviolet detection using on-line complexation with Cu(II) ion for analysis of five alcohols including diols and triol (methanol, ethanol, 1,2-propanediol, 1,3-propanediol, and glycerol). The Cu(II) ion concentration in the mobile phase had a great influence on the peak areas of these alcohols, but not on their retention times. Column temperature (25 − 40°C) and pH of the mobile phase did not affect the separation of analytes. The optimum separation conditions were determined as 5 mM CuSO4, 3 mM H2SO4, and 3 mM NaOH at 30°C. The ratio of the peak areas for three alcohols (methanol, 1,2-propanediol, and glycerol) was in good agreement with that calculated from the obtained stability constants, molar absorption coefficients for the 1:1 Cu(II) complexes with the three alcohols, and the injected molar quantities. This fact strongly suggests that the observed high-performance liquid chromatography signals resulted from formation of the 1:1 Cu(II)–alcohol complexes. Using the proposed method, these five alcohols in spirit, liquid for electronic cigarette, mouthwash, and nail enamel remover samples were successfully analyzed with only a simple pretreatment. This article is protected by copyright. All rights reserved



pH-zone-refining elution-extrusion countercurrent chromatography: Separation of hydroxyanthraquinones from Cassiae Semen

2017-08-28T01:50:26.903485-05:00

Seven hydroxyanthraquinones were successfully separated from the traditional Chinese medicinal herb Cassiae Semen by conventional and pH-zone-refining countercurrent chromatography with an environmentally friendly biphasic solvent system, in which elution–extrusion mode was investigated for pH-zone-refining countercurrent chromatography for the first time. A two-phase solvent system composed of n-hexane/ethyl acetate/ethanol/water (5:3:4:4, v/v) was used for the conventional countercurrent chromatography while the same system with a different volume ratio n-hexane/ethyl acetate/ethanol/water (3:5:2:6, v/v) was used for pH-zone-refining countercurrent chromatography, in which 20 mmol L−1 of trifluoroacetic acid was added in the organic phase as a retainer and 15 mmol L−1 of ammonia was added to the aqueous phase as an eluter. A 400 mg crude sample could be well separated by pH-zone-refining countercurrent chromatography, yielding 53 mg of aurantio-obtusin, 40 mg of chryso-obtusin, 18 mg of obtusin, 24 mg of obtusifolin, 10 mg of emodin and 105 mg the mixture of chrysophanol and physcion with a purity of over 95.8, 95.7, 96.9, 93.5, 97.4, 77.1 and 19.8%, as determined by high-performance liquid chromatography. Furthermore, the difference in elution sequence between conventional and pH-zone-refining mode was observed and discussed. This article is protected by copyright. All rights reserved



Enantioselective determination of 1-[4-(2-methoxyethyl)phenoxy]-3-[2-(2-methoxyphenoxy)ethylamino]-2-propanol hydrochloride, a novel antihypertensive agent, in rat plasma and tissues by LC–MS/MS

2017-08-28T01:50:19.78547-05:00

Enantioselective biodistribution studies of 1-[4-(2-methoxyethyl)phenoxy]-3-[2-(2-methoxyphenoxy)ethylamino]-2-propanol hydrochloride (TJ0711), a novel antihypertensive agent, require the accurate and precise quantification of each TJ0711 enantiomer in biological fluids and tissues. Here we report a simple and sensitive liquid chromatography with tandem mass spectrometry method for simultaneous determination of (R)-TJ0711 and (S)-TJ0711 in rat plasma and tissue samples using protein precipitation. The influence of column type, temperature, mobile phase composition, and flow rate on the retention and enantioselectivity was evaluated. The separation of the TJ0711 enantiomers was ultimately achieved on a SUMICHIRAL OA-2500 column in 15 min using isocratic elution with ethanol/hexane (40:60) at a flow rate of 0.8 mL/min. Good linearities of spiked analyte concentration from 5 to 2000 ng/mL were achieved and the correlation coefficients (R) were greater than 0.99. The intra- and inter-day accuracy and precision for both analytes were less than 15% at all concentration levels, and the extraction recoveries were consistent among the five quality control concentrations. This assay was successfully applied to quantify plasma and tissue concentrations of TJ0711 enantiomers in a preclinical study. This article is protected by copyright. All rights reserved



Stereoselective determination of dufulin in watermelon under field conditions using chiral ultra high performance liquid chromatography with high-resolution mass spectrometry

2017-08-26T08:50:23.107765-05:00

An effective and sensitive chiral analytical method was established to investigate the stereoselective dissipation of rac-dufulin in watermelon using ultra-high-performance liquid chromatography with a Superchiral S-OD chiral column (4.6 mm × 150 mm i.d., 5 μm) coupled with high-resolution mass spectrometry. To optimize the pretreatment method for detecting rac-dufulin in the three matrices, different extraction solvents, extractant volumes, extraction times, and absorbents were investigated to improve extraction efficiency. Moreover, analysis of variance was used to perform method validation for determination of the two dufulin enantiomers in the three matrices. Using the optimized method, good linearity was obtained (determination coefficient > 0.999). The limits of detection and quantification of the two dufulin enantiomers in soil, watermelon, and pulp were 0.15 and 0.5 μg/kg, respectively. The average recoveries of the two enantiomers in the three matrices at four spiked levels ranged from 75.0 to 107.8%, with intra- and inter-day relative standard deviations of 0.4–10.4%. In field trials, the R enantiomer was preferentially dissipated in watermelon. These method validation results confirmed that the developed method was convenient and reliable for the stereoselective determination of enantiomers of rac-dufulin in watermelon. This article is protected by copyright. All rights reserved



High-throughput LC–MS method for the rapid characterization of multiple chemical constituents and metabolites of Da-Bu-Yin-Wan

2017-08-25T07:45:24.129899-05:00

Traditional Chinese medicine is the clinical experience accumulated by Chinese people against diseases. Da-Bu-Yin-Wan is a famous traditional Chinese medicine formula consisting of Phellodendri amurensis Rupr., Anemarrhenae asphodeloides Bge., Radix Rehmanniae Preparata and Chinemys reevesii. In this study, ultra high performance liquid chromatography equipped with electrospray ionization quadrupole time-of-flight high-definition mass spectrometry with the controlled software of Masslynx (V4.1) was established for comprehensive screen and identified the chemical constituents and serum metabolites of Da-Bu-Yin-Wan in vivo and in vitro. Consequently, 70 peaks in the methanol extract from Da-Bu-Yin-Wan and 38 peaks absorbed into rat blood were characterized. The 70 constituents in vitro included alkaloids, flavonoids, polysaccharide, limonoids, flavonoid, etc. And the 38 constituents were consists of 22 absorbed prototype and 16 metabolites of Da-Bu-Yin-Wan absorbed in vivo. We fully clarified the chemical constituents of Da-Bu-Yin-Wan and provided a scientific strategy for screening and characterization the chemical constituents and metabolites of traditional Chinese medicine in vitro and in vivo. This article is protected by copyright. All rights reserved



Qualitative and quantitative determination of YiXinShu Tablet using ultra high performance liquid chromatography with Q Exactive hybrid quadrupole orbitrap high-resolution accurate mass spectrometry

2017-08-24T13:50:26.277405-05:00

To clarify and quantify the chemical profile of YiXinShu Tablet rapidly, a feasible and accurate strategy was developed by applying ultra high performance liquid chromatography with Q Exactive hybrid quadrupole orbitrap high-resolution accurate mass spectrometry. A total of 105 components were identified, including 25 phenanthraquinones, 11 lactones, 19 lignans, 24 acids and 26 other compounds. Among them, 26 major compounds were unambiguously detected by comparing with reference standards. And 19 of these compounds in three batches of YiXinShu Tablet were selected for quantitative determination. (Z)-Ligustilide, salvianic acid A, salvianolic acid A, salvianolic acid B and rosmarinic acid were abundant in these three batches with contents over 1.000 mg/g. The established analysis methods were examined to be accurate and feasible. The results show that the ultra high performance liquid chromatography with Q Exactive hybrid quadrupole orbitrap high-resolution accurate mass spectrometry method has a powerful qualitative ability and promising quantitative application. This article is protected by copyright. All rights reserved



Magnetic micro-solid-phase extraction based on magnetite-mcm-41 with GC–MS for the determination of anti-depressant drugs in biological fluids

2017-08-24T09:55:29.917926-05:00

A new facile magnetic micro-solid-phase extraction coupled to gas chromatography and mass spectrometry detection was developed for extraction and determination of selected anti-depressant drugs in biological fluids using magnetite-MCM-41 as adsorbent. The synthesized sorbent was characterized by several spectroscopic techniques. The maximum extraction efficiency for extraction of 500 μg/L anti-depressant drugs from aqueous solution was obtained with 15 mg of magnetite-MCM-41 at pH 12. The analyte was desorbed using 100 μL of acetonitrile prior to gas chromatography determination. This method was rapid where the adsorption procedure was completed in 60 s. Under the optimized conditions using 15 mL of anti-depressant drugs sample, the calibration curve showed good linearity in the range of 0.05–500 μgL−1 (r2 = 0.996-0.999). Good limits of detection (0.008–0.010 μgL−1) were obtained for the analytes with good relative standard deviations of < 8.0 % (n = 5) for the determination of 0.1, 5.0 and 500.0 μgL−1 of anti-depressant drugs This method was successfully applied to the determination of amitriptyline and chlorpromazine in plasma and urine samples. The recoveries of spiked plasma and urine samples were in the range of 86.1–115.4%. Results indicate that magnetite micro-solid-phase extraction with gas chromatography and mass spectrometry is a convenient, fast, and economical method for the extraction and determination of amitriptyline and chlorpromazine in biological samples. This article is protected by copyright. All rights reserved



Advances in organic–inorganic hybrid sorbents for the extraction of organic and inorganic pollutants in different types of food and environmental samples

2017-08-21T04:31:01.708911-05:00

The efficiency of the extraction and removal of pollutants from food and the environment has been an important issue in analytical science. By incorporating inorganic species into an organic matrix, a new material known as an organic–inorganic hybrid material is formed. As it possesses high selectivity, permeability as well as mechanical and chemical stabilities, organic–inorganic hybrid materials constitute an emerging research field and have become popular to serve as sorbents in various separations science methods. Here, we review recent significant advances in analytical solid-phase extraction employing organic–inorganic composite/nanocomposite sorbents for the extraction of organic and inorganic pollutants from various types of food and environmental matrices. The physicochemical characteristics, extraction properties and analytical performances of sorbents are discussed; including morphology and surface characteristics, types of functional groups, interaction mechanism, selectivity and sensitivity, accuracy and regeneration abilities. Organic–inorganic hybrid sorbents combined with extraction techniques are highly promising for sample preparation of various food and environmental matrixes with analytes at trace levels. This article is protected by copyright. All rights reserved



GC–MS/MS method for the determination and pharmacokinetic analysis of borneol and muscone in rat after the intravenous administration of Xingnaojing injection

2017-08-19T06:20:23.497707-05:00

A simple and sensitive gas chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of borneol and muscone in rat plasma. The analytes and internal standard, naphthalene, were extracted using a convenient one-step liquid–liquid extraction method with ethyl acetate. The chromatographic separation was realized on a HP-5MS capillary column and detected in multiple reaction monitoring mode. Excellent linearity (R2 ≥ 0.996) was shown over 10.0–5000 ng/mL for borneol and 2.5–250 ng/mL for muscone. The lower limit of quantitation was 10 and 2.5 ng/mL for borneol and muscone, respectively. The intra- and inter-day precisions were less than 7.52%, and the accuracy values were between –8.03 and 14.52%. The extraction recovery, matrix effect and stability were sufficient to meet the Food and Drug Administration criteria. Meanwhile, the assay was successfully applied to the pre-clinical pharmacokinetic study of borneol and muscone following intravenous administration of Xingnaojing injection, a modern Chinese herbal medicine preparation. This article is protected by copyright. All rights reserved



Electrospun magnetic polybutylene terephethalate nanofibers for thin-film microextraction

2017-07-31T05:20:33.200988-05:00

A thin-film microextraction method using elecrospun magnetic polybutylene terephthalate nanofibers is developed and implemented to isolate some selected triazines. Due to the high mechanical stability of these nanofibers, they are repeatedly used under harsh magnetic stirring and ultrasonic conditions without any damage and structure degradation. The presence of magnetic nanoparticles within the nanofiber structure, increases the extraction efficiency while the fibers could be collected by an external magnet. The synthesized nanocomposite showed strong affinity toward the selected analytes. Apart from the concentration of magnetic nanoparticles within the nanocomposite network, the effect of different parameters on the extraction and desorption processes including the sample pH, extraction time, sample volume, type of desorption solvent, solvent volume and desorption time were optimized. Eventually, the detection limits were in the range of 0.02–0.05 ng mL−1, while the limits of quantification were between 0.1 and 0.2 ng mL−1. The linear dynamic range was 0.1–100 ng mL−1 and the relative standard deviations were 4–9% (n = 3). The developed method was extended to the real water samples and the relative recoveries were in the range of 86–103%, indicating that the prepared sorbent is suitable for extraction of triazines from environmental samples. This article is protected by copyright. All rights reserved



Development and validation of a subcritical 1,1,1,2-tetrafluoroethane extraction technique: GC–MS method for the simultaneous determination of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and polybrominated biphenyl ethers in aquatic products

2017-07-26T01:50:55.111069-05:00

A simple, rapid and green method was developed for the simultaneous analysis of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and polybrominated biphenyl ethers in aquatic products using subcritical 1,1,1,2-tetrafluoroethane extraction coupled with gas chromatography and mass spectrometry. Effects of the extraction temperature, pressure and co-solvent volume on the extraction efficiency were investigated by extracting spiked oyster samples. The results show that the maximum extraction efficiency was obtained at 40°C, 12 MPa and a co-solvent (dichloromethane) volume of 5.0 mL. Under these conditions, the calibration curves had good linearity with square of the correlation larger than 0.998 in the concentration range of 5–800 ng mL−1; limit of detection and limit of quantitation were 0.16–2.83 and 0.55–9.43 ng g−1, respectively. At spiked levels of 10, 30 and 50 ng g−1, the average recoveries were 70.4–80.4% for polycyclic aromatic hydrocarbons, 74.0–83.6% for polychlorinated biphenyls and 66.9–78.0% for polybrominated biphenyl ethers, with average relative standard deviations of less than 16.3%. The established method has no significant differences in recovery compared to traditional methods and is suitable for the analysis of real samples. This article is protected by copyright. All rights reserved



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

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

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



Study of organic acids in Schisandrae Chinensis Fructus after vinegar processing

2017-09-22T07:40:43.713982-05:00

The ripened fruit of Schisandrae Chinensis Fructus has unique medical properties in Chinese medicine. It is commonly used after vinegar steaming. Vinegar steaming changes the color of Schisandrae Chinensis Fructus from red to black and enhances its acidic and astringent properties. Lignans are the well-investigated components in this herb. However, Schisandrae Chinensis Fructus is acidic in the theory of Chinese medicine, and whether vinegar processing changes its organic acid components remains largely unknown. In this study, the organic acids in this herb were derived by the method of methyl esterification, and further analyzed by gas chromatography with mass spectrometry. A total of 39 organic acid compounds were identified. Interestingly, Schisandrae Chinensis Fructus after vinegar processing showed a significant increase in the content of levulinic acid as compared to the unprocessed ones. Pharmacological experiments demonstrated that levulinic acid inhibited the contractility of isolated intestine and had an inhibitory effect on the excessive hyperfunction of small intestinal propulsion. Moreover, the extracts of vinegar-processed Schisandrae Chinensis Fructus had a stronger inhibitory on the excessive hyperfunction of small intestinal propulsion than that of unprocessed ones. Taken together, this study offers novel insight into the effect of Schisandrae Chinensis Fructus after vinegar processing.



Polypyrrole-magnetite dispersive micro-solid-phase extraction combined with ultraviolet-visible spectrophotometry for the determination of rhodamine 6G and crystal violet in textile wastewater

2017-09-22T07:40:26.527287-05:00

Polypyrrole-magnetite dispersive micro-solid-phase extraction method combined with ultraviolet-visible spectrophotometry was developed for the determination of selected cationic dyes in textile wastewater. Polypyrrole-magnetite was used as adsorbent due to its thermal stability, magnetic properties, and ability to adsorb Rhodamine 6G and crystal violet. Dispersive micro-solid-phase extraction parameters were optimized, including sample pH, adsorbent amount, extraction time, and desorption solvent. The optimum polypyrrole-magnetite dispersive micro-solid phase-extraction conditions were sample pH 8, 60 mg polypyrrole-magnetite adsorbent, 5 min of extraction time, and acetonitrile as the desorption solvent. Under the optimized conditions, the polypyrrole-magnetite dispersive micro-solid-phase extraction with ultraviolet-visible method showed good linearity in the range of 0.05–7 mg/L (R2 > 0.9980). The method also showed a good limit of detection for the dyes (0.05 mg/L) and good analyte recoveries (97.4–111.3%) with relative standard deviations < 10%. The method was successfully applied to the analysis of dyes in textile wastewater samples where the concentration found was 1.03 mg (RSD ±7.9%) and 1.13 mg/L (RSD ± 4.6%) for Rhodamine 6G and crystal violet, respectively. It can be concluded that this method can be adopted for the rapid extraction and determination of dyes at trace concentration levels.



Magnetic dispersive solid-phase extraction based on modified magnetic nanoparticles for the detection of cocaine and cocaine metabolites in human urine by high-performance liquid chromatography–mass spectrometry

2017-09-22T07:37:16.583602-05:00

An easy-to-handle magnetic dispersive solid-phase extraction procedure was developed for preconcentration and extraction of cocaine and cocaine metabolites in human urine. Divinyl benzene and vinyl pyrrolidone functionalized silanized Fe3O4 nanoparticles were synthesized and used as adsorbents in this procedure. Scanning electron microscopy, vibrating sample magnetometry, and infrared spectroscopy were employed to characterize the modified adsorbents. A high-performance liquid chromatography with mass spectrometry method for determination of cocaine and its metabolites in human urine sample has been developed with pretreatment of the samples by magnetic dispersive solid-phase extraction. The obtained results demonstrated the higher extraction capacity of the prepared nanoparticles with recoveries between 75.1 to 105.7% and correlation coefficients higher than 0.9971. The limits of detection for the cocaine and cocaine metabolites were 0.09–1.10 ng/mL. The proposed magnetic dispersive solid-phase extraction method provided a rapid, environmentally friendly and magnetic stuff recyclable approach and it was confirmed that the prepared adsorbents material was a kind of highly effective extraction materials for the trace cocaine and cocaine metabolites analyses in human urine.



Orthogonal strategy development using reversed macroporous resin coupled with hydrophilic interaction liquid chromatography for the separation of ginsenosides from ginseng root extract

2017-09-22T07:35:26.323939-05:00

Ginsenosides have been widely conceded as having various biological activities and are considered to be the active ingredient of ginseng. Nowadays, preparative high-performance liquid chromatography is considered to be a highly efficient method for ginseng saponins purification and preparation. However, in the process of practical application, due to the complex and varied composition of natural products and relatively simple pretreatment process, it is likely to block the chromatographic column and affect the separation efficiency and its service life. In this work, an orthogonal strategy was developed; in the first-dimension separation, reverse-phase macroporous resin was applied to remove impurities in ginseng crude extracts and classified ginseng extracts into protopanaxatriol and protopanaxadiol fractions. In the second-dimension separation, the obtained fractions were further separated by a preparative hydrophilic column, and finally yielded 11 pure compounds. Eight of them identified as ginsenoside Rh1, Rg2, Rd, Rc, Rb2, Rb1, Rg1, and Re by standards comparison and electrospray ionization mass spectrometry. The purity of these ginsenosides was assessed by high-performance liquid chromatography with UV detection.



Simple and sensitive determination of malondialdehyde in human urine and saliva using UHPLC–MS/MS after derivatization with 3,4-diaminobenzophenone

2017-09-22T07:30:35.395287-05:00

Malondialdehyde has been used as a biomarker for lipid peroxidation in biological samples. An ultra-high performance liquid chromatography with tandem mass spectrometry method was developed to determine the levels of malondialdehyde in human urine and saliva samples. To select the optimum derivatization reagent from four diamino compounds, the reactivity and sensitivity of their derivatives were compared, and 3,4-diaminobenzophenone was selected. The optimum reaction conditions for malondialdehyde with 3,4-diaminobenzophenone were as follows: a reagent dosage of 50 mg/L, pH of 4, and reaction for 30 min at 50°C. The formed derivative product was analyzed using ultra-high performance liquid chromatography with tandem mass spectrometry without additional extraction or concentration steps. In the optimal conditions, the method was used to determine malondialdehyde concentration in human urine and saliva samples. The limits of quantification for malondialdehyde in biological samples were over a concentration range of 0.1–0.3 μg/L. Additionally, the calibration curve showed a linearity greater than r2 = 0.997. The method was used to analyze 14 human urine and saliva samples from healthy volunteers. Malondialdehyde was detected in the concentration range of 1.7–33.6 μg/g creatinine in all human urine samples and 0.1–1.3 μg/L in all human saliva samples.



Determination of betaine, l-carnitine, and choline in human urine using a self-packed column and column-switching ion chromatography with nonsuppressed conductivity detection

2017-09-21T00:51:06.427716-05:00

A simple method for the determination of betaine, l-carnitine, and choline in human urine was developed based on column-switching ion chromatography coupled with nonsuppressed conductivity detection by using a self-packed column. A pretreatment column (50 mm × 4.6 mm, id) packed with poly(glycidyl methacrylate-divinylbenzene) microspheres was used for the extraction and cleanup of analytes. Chromatographic separation was achieved within 10 min on a cationic exchange column (150 mm × 4.6 mm, id) using maleic anhydride modified poly(glycidyl methacrylate-divinylbenzene) as the particles for packing. The detection was performed by ion chromatography with nonsuppressed conductivity detection. Parameters including column-switching time, eluent type, flow rates of eluent, and interfering effects were optimized. Linearity (r2 ≥ 0.99) was obtained for the concentration range of 0.50–100, 0.75–100, and 0.25–100 μg/mL for betaine, l-carnitine, and choline, respectively. Detection limits were 0.12, 0.20, and 0.05 μg/mL for betaine, l-carnitine, and choline, respectively. The intra- and interday accuracy and precision for all quality controls were within ±10.11%. Satisfactory recovery was observed between 92.5 and 105.0%. The validated method was successfully applied for the determination of betaine, l-carnitine, and choline in urine samples from healthy people.



Monitoring quality consistency of Liuwei Dihuang Pill by integrating the ultraviolet spectroscopic fingerprint, a multi-wavelength fusion fingerprint method, and antioxidant activities

2017-09-21T00:50:52.355445-05:00

Liuwei Dihuang Pill, a classical traditional Chinese medicine, has been widely used to treat kidney yin deficiency in China for hundreds of years. Little attention, however, has been paid to quality control methods for this formulation. In the present study, we aimed to establish a comprehensive and practical quality evaluation system for Liuwei Dihuang Pill. Thus, ultraviolet spectroscopic fingerprints and multi-wavelength fusion fingerprints have been proposed for quality consistency evaluation of the popular patent. The similarity analysis of Liuwei Dihuang Pill samples was evaluated by systematic quantitative fingerprint method from qualitative and quantitative perspectives. The results showed that 26 batches of samples were classified into five grades for fusion fingerprints and three grades for ultraviolet spectroscopic fingerprints. Moreover, the fingerprint–efficacy correlation was also established and confirmed through the partial least squares model to visualize the antioxidant activity of Liuwei Dihuang Pill in vitro. In conclusion, these results indicated that integrating ultraviolet spectroscopic fingerprints and multi-wavelength fusion fingerprints coupled with antioxidant activities provide a rapid and effective approach to monitor the quality consistency of Liuwei Dihuang Pill.



Magnetic ionic liquid assisted single-drop microextraction of ascorbic acid before its voltammetric determination

2017-09-13T00:51:53.045322-05:00

For the first time, we coupled a microextraction technique using a magnetic ionic liquid with voltammetric determination. A hydrophobic magnetic ionic liquid that contains the tetrachloromanganate(II) anion, namely, aliquat tetrachloromanganate(II), was synthesized and used for the extraction of ascorbic acid from aqueous solutions followed by voltammetric determination. The extraction procedure was carried out using a single drop microextraction technique in which the ascorbic acid containing magnetic ionic liquid was separated with a magnet and then cast onto the surface of a carbon paste electrode modified with TiO2 nanoparticles for the voltammetric quantification of the extracted ascorbic acid. Electrochemical quantification was carried out in a blank phosphate buffer solution. After optimizing different experimental conditions, a linear concentration range of 1.50–40.0 nM with a detection limit of 0.43 nM was obtained for the determination of ascorbic acid. The presented approach was successfully applied to the determination of ascorbic acid in samples of vitamin C effervescent tablets and orange juice.



Use of Ionic liquids as additives in ion exchange chromatography for the analysis of cations

2017-09-13T00:51:24.900483-05:00

The behavior of acids (citric acid, nitric acid, oxalic acid, tartaric acid) as a mobile phase and imidazolium ionic liquids (the bromides, tetrafluoroborates and hexafluorophosphates of 1-ethyl, 1-butyl, and 1-hexyl-3-methylimidazolium) as additives in ion exchange chromatography for cations (Na+, K+, Mg2+, Ca2+) separation were studied. The results showed that nitric acid and 1-hexyl-3-methyl-imidazolium hexafluorophosphate offered the most interesting features in the separation of cations, such as lower retention time and better resolution. The selected optimal conditions were achieved by adding 0.10 mM 1-hexyl-3-methyl-imidazolium hexafluorophosphate in 4.0 mM HNO3 mobile phase for the separation of four cations with the flow rate of 0.9 mL/min at room temperature (25°C). The linear regression equations of Na+, K+, Mg2+, Ca2+ were S = 4.4763c + 0.0209, S = 3.8903c – 0.0087, S = 6.3974c – 0.0173, and S = 7.601c – 0.0339 and the limits of detection of Na+, K+, Mg2+, Ca2+ were 0.296, 4.98, 0.0970, and 1.22 μg/L, respectively. In this work, four cations in samples were successfully detected.



The stochastic resonance algorithm with the direct current signal as external force and its application to the detection of weak chromatographic peaks

2017-09-13T00:50:52.653443-05:00

As a potential tool for amplifying weak chromatographic peaks, the stochastic resonance algorithm was developed based upon a counterintuitive physical phenomenon. Therefore, the essential step, parameter optimization, was perplexing and difficult for analysts. In order to avoid optimizing the system parameters on a case-by-case basis, an improved algorithm was proposed by introducing a constant or direct current signal into the signal to be measured as the external force. The weak chromatographic peak can be amplified and detected by the new algorithm using the same set of parameters. Two sets of our previous experimental data were reanalyzed by using the developed algorithm and the results were satisfactory. A generalized solution was expected to come into being on account of the new algorithm.



A flow-through column electrolytic cell for supercritical fluid chromatography*

2017-09-12T08:25:43.891351-05:00

A novel flow-through column electrolytic cell was proposed as a detector to obtain current signals for supercritical fluid chromatography. The electrochemical cell consisted of two electrodes and its holder, and a working and a counter electrode were fabricated from 192 carbon strings, which were composed of 400 carbon fibers of 10 μm in diameter filled into a heat-shrinkable tube. These electrodes were placed in the center of a holder made from polyether ether ketone blocks and they were separated by polytetrafluoroethylene membrane filters. To evaluate the sensitivity of this cell, a standard solution of ferrocene was injected into the supercritical fluid chromatography system connected to the electrolytic cell. The ferrocene was eluted through a silica gel column using a mixture of a mobile phase of supercritical CO2 and a modifier of methanol containing ammonium acetate. The current peak area of ferrocene correlated to the ferrocene concentration in the range of 10–400 μmol/L (r = 0.999). Moreover, the limit of detection on the column estimated from a signal-to-noise ratio of 3 was 9.8  × 10−13 mol.



Evaluation of poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) cationic polymer capillary coating for capillary electrophoresis and electrokinetic chromatography separations

2017-09-11T04:25:46.534229-05:00

Capillary electrophoresis and electrokinetic chromatography are typically carried out in unmodified fused-silica capillaries under conditions that result in a strong negative zeta potential at the capillary wall and a robust cathodic electroosmotic flow. Modification of the capillary wall to reverse the zeta potential and mask silanol sites can improve separation performance by reducing or eliminating analyte adsorption, and is essential when conducting electrokinetic chromatography separations with cationic latex nanoparticle pseudo-stationary phases. Semipermanent modification of the capillary walls by coating with cationic polymers has proven to be facile and effective. In this study, poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymers were synthesized by reversible addition-fragmentation chain transfer polymerization and used as physically adsorbed semipermanent coatings for capillary electrophoresis and electrokinetic chromatography separations. An initial synthesis of poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymer coating produced strong and stable anodic electroosmotic flow of –5.7 to –5.4 × 10−4 cm2/V⋅s over the pH range of 4–7. Significant differences in the magnitude of the electroosmotic flow and effectiveness were observed between synthetic batches, however. For electrokinetic chromatography separations, the best performing batches of poly([2-(acryloyloxy)ethyl]trimethylammonium chloride) polymer performed as well as the commercially available cationic polymer polyethyleneimine, whereas polydiallylammonium chloride and hexadimethrine bromide did not perform well.



Simple and rapid determination of zaltoprofen in human plasma by manual-shaking-assisted dispersive liquid–liquid microextraction followed by liquid chromatography with ultraviolet detection

2017-09-11T04:25:40.357992-05:00

A readily applicable method was developed to determine the concentration level of zaltoprofen, a non-steroidal antiinflammatory drug from the propionic acid family, in human plasma. This method is based on manual-shaking-assisted dispersive liquid–liquid microextraction coupled with liquid chromatography with ultraviolet detection. Factors affecting the extraction efficiency were screened and optimized by experimental design using fractional factorial and central composite designs, respectively. Optimal conditions were: 220 μL of C2H4Cl2 (extraction solvent), 5 mL of 3.75% w/v NaCl aqueous solution at pH 2.0, and manual shaking for 13 s (65 times). The resulting extraction method yielded a reasonable enrichment factor of 18.0 (±0.6, n = 3) and extraction recovery of 86.0% (±3.3%, n = 3). The established method was validated for selectivity, linearity, precision, accuracy, matrix effect, recovery, dilution integrity, and stability, and it met the acceptable criteria for all of the tested parameters. Specifically, the method was linear in the range of 0.16–50.0 mg/L, precise (< 8.8% RSD), accurate (–7.5–5.6% deviation), and showed negligible matrix effects (96.1–106.4%) with high absolute recovery (94.5–97.7%). Compared with previous methods involving labor-intensive liquid–liquid extraction or non-specific protein precipitation, our method allows the simple, rapid, and efficient determination of zaltoprofen using the most affordable analytical instrument, liquid chromatography with ultraviolet detection.



Determination of fat- and water-soluble vitamins by supercritical fluid chromatography: A review

2017-09-11T04:25:34.332901-05:00

Vitamins are compounds that take part in all basic functions of an organism but also are subject of number of studies performed by different researchers. Two groups of vitamins are distinguished taking into consideration their solubility. Chromatography with supercritical CO2 has found application in the determination, separation, and quantitative analyses of both fat- and water-soluble vitamins. The methods of vitamins separation have developed and improved throughout the years. Both groups of compounds were separated using supercritical fluid chromatography with different detection on different stationary phases. The main aim of this review is to provide an overview of the studies of vitamins separation that have been determined so far.



Simultaneous determination of ferulic acid and gastrodin of Tianshu Capsule in rat plasma by ultra-fast liquid chromatography with tandem mass spectrometry and its application to a comparative pharmacokinetic study in normal and migraine rats

2017-09-11T04:12:23.997175-05:00

Tianshu Capsule, consisting of Ligusticum chuanxiong Hort and Gastrodia elata Blume, is a widely used Traditional Chinese Medicine preparation for the treatment of migraine. Ferulic acid and gastrodin are main active constituents in Ligusticum chuanxiong Hort and Gastrodia elata Blume, and have been used as marker components for quality control of Tianshu Capsule. In this study, a selective, sensitive, and reliable ultra-fast liquid chromatography with tandem mass spectrometry method was developed for simultaneous determination of ferulic acid and gastrodin in rat plasma using geniposide as internal standard. The plasma samples were extracted by protein precipitation with methanol after acidification and separated on a Shim-Pack XR-ODS C18 column (75 × 3.0 mm, 2.2 μm) using gradient elution with a mobile phase consisting of water (containing 0.1% formic acid) and acetonitrile at a flow rate of 0.6 mL/min. Detection was performed on 3200 QTRAP mass spectrometry equipped with turbo ion spray source in negative ionization mode. Validation parameters were within acceptable ranges. The validated method was applied to compare the pharmacokinetic profiles of ferulic acid and gastrodin in normal and migraine rats. Our results showed that there were remarkable differences in the pharmacokinetic properties of the analytes between the normal and migraine groups.



Evaluation and quantitative analysis of 11 compounds in Morinda officinalis using ultra-high performance liquid chromatography and photodiode array detection coupled with chemometrics

2017-09-11T04:11:55.840079-05:00

Morinda officinalis (Rubiaceae) is a traditional Chinese medicine widely used for the treatment of impotence and osteoporosis in clinical therapy. In the present study, a rapid and simple ultra-high performance liquid chromatography with photodiode array detection method was developed and validated for the simultaneous determination of 11 bioactive compounds in M. officinalis. This assay method was validated with respect to linearity (R2 > 0.9991), precision, repeatability, limit of detection, limit of quantification, and accuracy (with observed recovery rates between 94.21 and 100.38%). The quantitative results revealed significant differences in the concentrations of the selected compounds. Additionally, chemometric methods, including hierarchical clustering analysis, principal component analysis, and partial least-squares discriminate analysis, were applied to compare and sort the 25 batches of M. officinalis samples based on the quantitative data of the analytes. All of the samples were clearly divided into two groups: the Hainan samples were successfully discriminated from the samples from other origins. Simultaneous determination of multiple compounds using the proposed method combined with chemometrics could be a viable strategy to compare and evaluate the quality of M. officinalis.






Simultaneous determination of the styrene unit content and assessment of molecular weight of triblock copolymers in adhesives by a size exclusion chromatography method

2017-09-07T11:30:30.830233-05:00

The content of styrene units in nonhydrogenated and hydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers significantly influences product performance. A size exclusion chromatography method was developed to determine the average styrene content of triblock copolymers blended with tackifier in adhesives. A complete separation of the triblock copolymer from the other additives was realized with size exclusion chromatography. The peak area ratio of the UV and refraction index signals of the copolymers at the same effective elution volume was correlated to the average styrene unit content using nuclear magnetic resonance spectroscopy with commercial copolymers as standards. The obtained calibration curves showed good linearity for both the hydrogenated and nonhydrogenated styrene-butadiene-styrene and styrene-isoprene-styrene triblock copolymers (r = 0.974 for styrene contents of 19.3–46.3% for nonhydrogenated ones and r = 0.970 for the styrene contents of 23–58.2% for hydrogenated ones). For copolymer blends, the developed method provided more accurate average styrene unit contents than nuclear magnetic resonance spectroscopy provided. These results were validated using two known copolymer blends consisting of either styrene-isoprene-styrene or hydrogenated styrene-butadiene-styrene and a hydrocarbon tackifying resin as well as an unknown adhesive with styrene-butadiene-styrene and an aromatic tackifying resin. The methodology can be readily applied to styrene-containing polymers in blends such as poly(acrylonitrile-butadiene styrene).



Sulfonated poly(styrene-divinylbenzene) modified with amines and the application for pipette-tip solid-phase extraction of carbendazim in apples

2017-09-05T09:03:51.688923-05:00

Sulfonated poly(styrene-divinylbenzene) modified with five kinds of amine functional groups was applied to the determination of carbendazim in apple samples with a pipette-tip solid-phase extraction method. The structures of the polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Five different modifications of the solid-phase extraction sorbent based on sulfonated poly(styrene-divinylbenzene) were tested under static and pipette-tip solid-phase extraction conditions. The polymer modified with p-methoxyaniline showed the best recognition capacity and adsorption amount for carbendazim. Under the optimum conditions, 3.00 mg of the adsorbent, 1.00 mL of ethyl acetate as washing solvent, and 1.00 mL of ammonia/acetonitrile (5:95, v/v) as elution solvent were used in the pretreatment procedure of apple samples. The calibration graphs of carbendazim in methanol were linear over 5.00–200.00 μg/mL, and the limits of detection and quantification were 0.01 and 0.03 μg/mL, respectively. The method recoveries of carbendazim were in the range of 91.31–98.13% with associated intraday relative standard deviations of 0.76–2.13% and interday relative standard deviations of 1.10–1.85%. Sulfonated poly(styrene-divinylbenzene) modified with p-methoxyaniline showed satisfactory results (recovery: 97.96%) and potential for the rapid purification of carbendazim in apple samples combined with the pipette-tip solid-phase extraction.



Screening bioactive quality control markers of QiShenYiQi dripping pills based on the relationship between the ultra-high performance liquid chromatography fingerprint and vascular protective activity

2017-09-05T09:03:40.059271-05:00

Traditional Chinese medicine consists of complex phytochemical constituents. Selecting appropriate analytical markers of traditional Chinese medicine is a critical step in quality control. Currently, the combination of fingerprinting and efficacy evaluation is considered as a useful method for screening active ingredients in complex mixtures. This study was designed to develop an orthogonal partial least squares model for screening bioactive quality control markers of QishenYiqi dripping pills based on the fingerprint–efficacy relationship. First, the chemical fingerprints of 49 batches of QishenYiqi dripping pill samples were established by ultra-high performance liquid chromatography coupled with a photodiode array detector. Second, ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry was exploited to systematically investigate the 36 copossessing fingerprint components in QishenYiqi dripping pills. The vascular protective activity of QishenYiqi dripping pills was determined by using a cell counting kit-8 assay. Finally, fingerprint–efficacy relationship was established by orthogonal partial least squares model. The results indicated that ten components exhibited strong correlation with vascular protective activity, and these were preliminarily screened as quality control markers. The present study provided a novel idea for the study of the pharmacodynamic material basis and quality evaluation of QishenYiqi dripping pills.



Supercritical fluid chromatography coupled with tandem mass spectrometry: A high-efficiency detection technique to quantify Taxane drugs in whole-blood samples

2017-09-05T08:55:35.918138-05:00

We present a technique to rapid determine taxane in blood samples by supercritical fluid chromatography together with mass spectrometry. The aim of this study was to develop a supercritical fluid chromatography with mass spectrometry method for the analysis of paclitaxel, cabazitaxel, and docetaxel in whole-blood samples of rats. Liquid-dry matrix spot extraction was selected in sample preparation procedure. Supercritical fluid chromatography separation of paclitaxel, cabazitaxel, docetaxel, and glyburide (internal standard) was accomplished within 3 min by using the gradient mobile phase consisted of methanol as the compensation solvent and carbon dioxide at a flow rate of 1.0 mL/min. The method was validated regarding specificity, the lower limit of quantification, repeatability, and reproducibility of quantification, extraction recovery, and matrix effects. The lower limit of quantification was found to be 10 ng/mL since it exhibited acceptable precision and accuracy at the corresponding level. All interday accuracies and precisions were within the accepted criteria of ±15% of the nominal value and within ±20% at the lower limit of quantification, implying that the method was reliable and reproducible. In conclusion, this method is a promising tool to support and improve preclinical or clinical pharmacokinetic studies with the taxanes anticancer drugs.



Numerical analysis of a dielectrophoresis field-flow fractionation device for the separation of multiple cell types

2017-09-04T08:26:15.208462-05:00

In this study, a dielectrophoresis field-flow fractionation device was analyzed using a numerical simulation method and the behaviors of a set of different cells were investigated. By reducing the alternating current frequency of the electrodes from the value used in the original setup configuration and increasing the number of exit channels, total discrimination in cell trajectories and subsequent separation of four cell types were achieved. Cells were differentiated based on their size and dielectric response that are represented in their real part of Clausius–Mossotti factor at different frequencies. A number of novel designs were also proposed based on the original setup configuration. It was seen that by reducing the length of the main channel and the number of electrodes at low frequencies and not changing the inlet flow velocities, cell separation was still achieved successfully, although with a slightly larger electrode voltage. The shorter main channel decreased the residence time for the cells on the chip and also reduced the overall size of the device—these were improvements over the original design. The obtained results can be used to analyze other cell types by knowing their size and dielectric properties to design geometries that can ensure separation.



Fast analysis of quaternary ammonium pesticides in food and beverages using cation-exchange chromatography coupled with isotope-dilution high-resolution mass spectrometry

2017-09-04T08:20:38.825373-05:00

A fast separation based on cation-exchange liquid chromatography coupled with high-resolution mass spectrometry is proposed for simultaneous determination of chlormequat, difenzoquat, diquat, mepiquat and paraquat in several food and beverage commodities. Solid samples were extracted using a mixture of water/methanol/formic acid (69.6:30:0.4, v/v/v), while liquid samples were ten times diluted with the same solution. Separation was carried out on an experimental length-modified IonPac CS17 column (2 × 15 mm2) that allowed the use of formic acid and acetonitrile as mobile phase. Detection limits for food and beverage matrices were established at 1.5 μg/L for chlormequat, difenzoquat and mepiquat, and 3 μg/L for diquat and paraquat, while for drinking water a pre-analytical sample concentration allowed detection limits of 9 and 20 ng/L, respectively. Precision, as repeatability (RSD%), ranged from 0.2 to 24%, with a median value of 6%, and trueness, as recovery, ranged from 64 to 118%, with a median value of 96%. The method developed was successfully applied to investigate the presence of herbicide residues in commercial commodities (mineral water, orange juice, beer, tea, green coffee bean, toasted coffee powder, cocoa bean, white corn flour, rice and sugar samples).



Development of a high-performance liquid chromatography procedure to identify known and detect novel C-13 oligosaccharide moieties in diterpene glycosides from Stevia rebaudiana (Bertoni) Bertoni (Asteraceae): Structure elucidation of rebaudiosides V and W

2017-09-01T06:35:40.765918-05:00

As an aid for structure elucidation of new steviol glycosides, reversed-phase C18 high-performance liquid chromatography method was developed with several previously characterized diterpene glycosides, to identify known and detect novel aglycone-C13 oligosaccharide moieties and indirectly identify C-19 interlinkages. Elution order of several diterpene glycosides and their aglycone-C13 oligosaccharide substituted with different sugar arrangements were also summarized. Comparison of the retention time of a product obtained after alkaline hydrolysis with the aglycone-C-13 portions of known compounds reported herein allowed us to deduce the exact positions of the sugars in the C-13 oligosaccharide portion. The elution position of several steviol glycosides with an ent-kaurene skeleton was helpful to describe an identification key. Two previously uncharacterized diterpene glycosides together with two known compounds were isolated from a commercial Stevia rebaudiana leaf extract. One was found to be 13-[(2-O-β-d-xylopyranosyl-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]ent-kaur-16-en-19-oic acid-(2-O-β-d-glucopyranosyl-β-d-glucopyranosyl) ester (rebaudioside V), whereas the other was determined to be 13-[(2-O-β-d-xylopyranosyl-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl)oxy]ent-kaur-16-en-19-oic acid-(2-O-α-l-rhamnopyranosyl-3-O-β-d-glucopyranosyl-β-d-glucopyranosyl) ester (rebaudioside W). Previously reported compounds were isolated in gram quantities and identified as rebaudioside J and rebaudioside H. In addition, a C-19 sugar-free derivative was also prepared from rebaudioside H to afford rebaudioside H1. Chemical structures were partially determined by the high-performance liquid chromatography method and unambiguously characterized by using one-dimensional and two-dimensional nuclear magnetic resonance experiments.



Extraction of ochratoxin A in red wine with dopamine-coated magnetic multi-walled carbon nanotubes

2017-08-31T10:56:39.702844-05:00

A new, rapid, green, and cost-effective magnetic solid-phase extraction of ochratoxin A from red wine samples was developed using polydopamine-coated magnetic multi-walled carbon nanotubes as the absorbent. The polydopamine-coated magnetic multi-walled carbon nanotubes were fabricated with magnetic multi-walled carbon nanotubes and dopamine by an in situ oxidative self-polymerization approach. Transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy and vibrating sample magnetometry were used to characterize the absorbents. Ochratoxin A was quantified with high-performance liquid chromatography coupled with fluorescence detection, with excitation and emission wavelengths of 338 and 455 nm, respectively. The conditions affecting the magnetic solid-phase extraction procedure, such as pH, extraction solution, extraction time, absorbent amount, desorption solution and desorption time were investigated to obtain the optimal extraction conditions. Under the optimized conditions, the extraction recovery was 91.8–104.5% for ochratoxin A. A linear calibration curve was obtained in the range of 0.1–2.0 ng/mL. The limit of detection was 0.07 ng/mL, and the limit of quantitation was 0.21 ng/mL. The recoveries of ochratoxin A for spiked red wine sample ranged from 95.65 to 100.65% with relative standard deviation less than 8%. The polydopamine-coated magnetic multi-walled carbon nanotubes showed a high affinity toward ochratoxin A, allowing selective extraction and quantification of ochratoxin A from complex sample matrixes.



Fingerprint profiles of flavonoid compounds from different Psidium guajava leaves and their antioxidant activities

2017-08-31T10:56:21.9025-05:00

Flavonoids are the main active components in Psidium guajava leaves and have many multi-physiological functions. In this study, the flavonoid compositions were identified in the Psidium guajava leaves samples using a high-performance liquid chromatography with time-of-flight electrospray ionization mass spectrometry method. A high-performance liquid chromatography fingerprint method, combined with chemometrics, was used to perform a quality assessment of the Psidium guajava leaves samples. The eight identified flavonoid compounds including rutin, isoquercitrin, quercetin-3-O-β-d-xylopyranoside, quercetin-3-O-α-l-arabinopyranoside, avicularin, quercitrin, quercetin, and kaempferol were used as the chemical markers. The antioxidant activity of 15 batches of samples was examined using three different methods, and the results revealed the Psidium guajava leaves samples that had higher contents of the flavonoid compounds, glycoside and aglycone, possessed the highest antioxidant capacities. Consequently, a combination of chromatographic fingerprints and chemometric analyses was used for a quality assessment of Psidium guajava leaf tea and its derived products, which can lay the foundation for the development of plant tea resources or other herbs.



Magnetic porous carbon derived from Co-doped metal–organic frameworks for the magnetic solid-phase extraction of endocrine disrupting chemicals

2017-08-31T10:56:10.128247-05:00

Metal–organic frameworks-5 (MOF-5) was explored as a template to prepare porous carbon due to its high surface area, large pore volume, and permanent nanoscale porosity. Magnetic porous carbon, Co@MOF-5-C, was fabricated by the one-step direct carbonization of Co-doped MOF-5. After carbonization, the magnetic cobalt nanoparticles are well dispersed in the porous carbon matrix, and Co@MOF-5-C displays strong magnetism (with the saturation magnetization intensity of 70.17emu/g), high-specific surface area, and large pore volume. To evaluate its extraction performance, the Co@MOF-5-C was applied as an adsorbent for the magnetic solid-phase extraction of endocrine disrupting chemicals, followed by their analysis with high-performance liquid chromatography. The developed method exhibits a good linear response in the range of 0.5–100 ng/mL for pond water and 1.0–100 ng/mL for juice samples. The limits of detection (S/N = 3) for the analytes were in the range of 0.1–0.2 ng/mL.



Ultra high performance liquid chromatography coupled with electrospray ionization/quadrupole time-of-flight mass spectrometry for the rapid analysis of constituents in the traditional Chinese medicine formula Wu Ji Bai Feng Pill

2017-08-31T10:56:03.08846-05:00

An ultra high performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry method in both positive and negative ion modes was established in order to comprehensively investigate the major constituents in Wu Ji Bai Feng Pill. Briefly, a Waters ACQUITY UPLC HSS C18 column was used to separate the aqueous extract of Wu Ji Bai Feng Pill. A total of 0.1% formic acid in acetonitrile and 0.1% aqueous formic acid v/v were used as the mobile phase. All analytes were determined using quadrupole time-of-flight mass spectrometry with electrospray ionization source in positive and negative ion modes. At length, a total of 173 components including flavones and their glycosides, monoterpene glycosides, triterpene saponins, phenethylalchohol glycosides, iridoid glycosides, phthalides, tanshinones, phenolic acids, sesquiterpenoids and cyclopeptides were identified or tentatively characterized in Wu Ji Bai Feng Pill in an analysis of 16.0 min based on the accurate mass and tandem mass spectrometry behaviors. The developed method is rapid and highly sensitive to characterize the chemical constituents of Wu Ji Bai Feng Pill, which could not only be used for chemical standardization and quality control of Wu Ji Bai Feng Pill, but also be helpful for further study in vivo metabolism of Wu Ji Bai Feng Pill.



Sensitive determination of typical phenols in environmental water samples by magnetic solid-phase extraction with polyaniline@SiO2@Fe as the adsorbents before HPLC

2017-08-31T10:55:54.628624-05:00

A novel magnetic core–shell material polyaniline@SiO2@Fe (PANI@SiO2@Fe) has been successfully synthesized and investigated as an effective adsorbent for the magnetic solid-phase extraction of typical endocrine disrupting compounds such as bisphenol A, tetrabromobisphenol A, and 4-nonylphenol from water samples. The morphology of the as-prepared PANI@SiO2@Fe was characterized by transmission electron microscopy and X-ray diffraction. The main parameters that influenced the enrichment performance such as the kind of eluent, amount of adsorbent, volume of eluent, adsorption time, elution time, ionic strength, pH, concentration of humic acid, and sample volume were investigated. Under the optimal conditions, a good linear relationship was found in the range of 0.05–100 μg/L for bisphenol A, 0.05–300 μg/L for tetrabromobisphenol A, and 0.05–250 μg/L for 4-nonylphenol, respectively. The correlation coefficients are all above 0.995. The limits of detection were in the range of 0.009–0.04 μg/L, and precisions were under 3.73% (n = 6). The real water analysis indicated that the spiked recoveries were in the range of 92.9–98.9% (n = 3). All these results indicated that the developed method was an efficient tool for the analysis of bisphenol A, tetrabromobisphenol A, and 4-nonylphenol.



Single standard substance for the determination of nine volatile components in the distillate of Fructus Gardeniae and Radix Curcumae (an intermediate of Xingnaojing Injection)

2017-08-31T10:55:43.502303-05:00

Xingnaojing Injection is a traditional Chinese medicine extensively used for stroke and cerebral ischemia. For better in-process quality control of Xingnaojing Injection, a method for the analysis of its intermediate (i.e., the distillate of Fructus Gardeniae and Radix Curcumae) is needed to monitor and optimize the hydrodistillation extraction process. In this work, nine major volatile components in the intermediate were identified: isophorone, 4-methylene-isophorone, curcumenone, curcumenol, curdione, curzerenone, furanodienone, curcumol, and germacrone. A quantitative analysis of multi-component with a single-marker method based on high-performance liquid chromatography with diode array detection was developed for the simultaneous determination of the nine components. In this method, only curdione was needed as the reference substance, and the other eight components were determined using their relative correction factors to curdione. In the method validation, good linearity (r > 0.9999), sensitivity, repeatability, and accuracy (recoveries within 95.3–105.4%) were shown. The repeatability and robustness of the relative correction factors were studied with different column temperatures, flow rates, detection wavelengths, columns, and instruments. In sample analyses, consistent results between the proposed method and the external standard method were shown. The proposed method provides a comprehensive and low-cost tool for the quality assessment of the intermediate of Xingnaojing Injection.



Comprehensive headspace gas chromatographic analysis of denaturants in denatured ethanol

2017-08-31T10:55:29.067462-05:00

To discourage consumption, ethanol is often denatured using both volatile (e.g., methyl ethyl ketone and isopropanol) and nonvolatile (e.g., denatonium benzoate) chemical substances. As a result, the analysis of denatured ethanol samples is usually performed by multiple techniques such as gas chromatography for the volatile denaturants and liquid chromatography for the nonvolatile ones. However, the need for multiple techniques increases the cost of analysis and forms a severe obstruction for on-site product control. Using the full evaporation technique combined with gas chromatography and flame ionization detection, only one analytical methodology has to be used here to determine both volatile and nonvolatile denaturants in denatured ethanol. Denatonium benzoate is determined as benzyl chloride following an in-vial reaction. Compared to conventional techniques, the novel method performs equally well, but it is simpler to apply. At the same time, drawbacks of alternative methods are circumvented such as equilibration issues and alterations to the stationary phase when using liquid chromatography with ion pairing agents or matrix effects when applying static headspace gas chromatography. The developed method showed good linearity, repeatability, and recovery toward all analytes and was applied to the analysis of commercial denatured ethanol for disinfection and ethanol-based windscreen washer fluids.



Simultaneous determination of simazine, cyanazine, and atrazine in honey samples by dispersive liquid–liquid microextraction combined with high-performance liquid chromatography

2017-08-31T01:55:26.574792-05:00

A rapid and simple sample preparation method was developed for simultaneous determination of three triazine herbicides in honey samples. The selected herbicides were extracted from honey samples by ionic liquid dispersive liquid–liquid microextraction, separated on a C18 column (250 mm × 4.6 mm id, 5 μm) using acetonitrile and H2O as the mobile phase with gradient elution, and then detected by high-performance liquid chromatography. The parameters, such as the type and volume of the extraction and disperser solvent, ion strength, pH, extraction time, and centrifuge time were optimized in order to provide the excellent extraction performance. Good linearity was showed for all the target herbicides over the tested concentration range with correlation coefficient higher than 0.994. Three spiked levels (0.005, 0.05, 0.10 mg/kg) were applied for determination of the recoveries of the targets in honey samples in the range of 80–103% with relative standard deviations not larger than 10.6%. The limits of quantification for the analytes ranged between 1.5 and 4.0 μg/kg. The developed method was applied for determination of the target compounds residues in real samples.



Sol–gel-adsorbent-coated extraction needles to detect volatile compounds in spoiled fish

2017-08-31T01:32:07.257689-05:00

Volatile compounds generated by fish spoilage were investigated by an inside-needle microextraction method followed by gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. The inside of a needle was coated with an adsorbent to extract the target analytes from the headspace of the sample. The examined adsorbents included β-cyclodextrin, polystyrene resin cross-linked with 1% divinylbenzene, and polyethylene glycol mixed with polydimethylsiloxane. The investigated volatile compounds generated by fish spoilage were acetone, 2-butanone, 2-butanol, 2-propanol, dimethyl disulfide, acetic acid, and benzaldehyde. The analysis conditions for the sorption and desorption processes were optimized. Each optimized condition was validated by determining the limit of detection and the limit of quantitation from the calibration curves, as well as the recovery, reproducibility, and concentration factors. As a result, all of the fabricated needles afforded successful recoveries, above 90%, with relative standard deviations below 10%. In particular, cyclodextrin and polystyrene resin cross-linked with 1% divinylbenzene mixed with polydimethylsiloxane show good sensitivities and concentration factors for the standard volatile compounds. The storage of fresh mackerel and salted mackerel at room temperature for 14 days caused the concentrations of dimethyl disulfide and acetic acid to significantly increase while those of acetone, 2-butanone, 2-propanol, and 2-butanol changed only slightly.



Postcolumn determination of polyphenolic antioxidants in Cirsium vulgare (Savi) Ten. extracts

2017-08-30T03:56:10.166674-05:00

Novel methods for the determination of polyphenolic antioxidants present in extracts from inflorescences of Cirsium vulgare (Savi) Ten. based on ultra-high performance liquid chromatography with photodiode array and chemiluminescence detection have been developed. Under the optimized conditions of chromatographic separation the analytical characteristic of the method was performed. The proposed method was successfully applied to the determination of ten polyphenols present in inflorescences of Cirsium vulgare. A comparison of the contents of analytes in extracts prepared by using various extraction media (methanol, ethanol, 70% methanol, 70% ethanol, and water) was carried out for the first time. For the postcolumn detection of scavenging activity of polyphenolic antioxidants against reactive oxygen species (H2O2, •OH, O2• −) three systems based on chemiluminescence of luminol were used. A review of the current scientific literature shows that this is the first report on the application of luminol-based postcolumn detection for the on-line investigation of •OH scavenging activity. The main compound determined in extracts from inflorescences of Cirsium vulgare was apigenin 7-O-glucuronide, whereas the highest antioxidant activity was observed for chlorogenic acid, luteolin 7-O-glucoside, and apigenin.



Preparative isolation of flavonoid glycosides from Sphaerophysa salsula using hydrophilic interaction solid-phase extraction coupled with two-dimensional preparative liquid chromatography

2017-08-30T03:46:32.702149-05:00

An offline preparative two-dimensional reversed-phase liquid chromatography/hydrophilic interaction liquid chromatography coupled with hydrophilic interaction solid-phase extraction method was developed for the preparative isolation of flavonoid glycosides from a crude sample of Sphaerophysa salsula. First, the non-flavonoids were removed using an XAmide solid-phase extraction cartridge. Based on the separation results of three different chromatographic stationary phases, the first-dimensional preparation was performed on an XAqua C18 prep column, and 15 fractions were obtained from the 5.2 g target sample. Then, three representative fractions were selected for additional purification on an XAmide preparative column to further isolate the flavonoid glycosides. In all, eight flavonoid glycosides were isolated in purities over 97%. The results demonstrated that the two-dimensional liquid chromatography method used in this study was effective for the preparative separation of flavonoid glycosides from Sphaerophysa salsula. Additionally, this method showed great potential for the separation of flavonoid glycosides from other plant materials.



Investigation of the continuous flow of the sample solution on the performance of electromembrane extraction: Comparison with conventional procedure

2017-08-29T03:30:48.053955-05:00

In this study, electromembrane extraction from a flowing sample solution, termed as continuous-flow electromembrane extraction, was developed and compared with conventional procedures for the determination of four basic drugs in real samples. Experimental parameters affecting the extraction efficiency were further studied and optimized. Under optimum conditions, linearity of continuous-flow procedure was within 8.0–500 ng/mL, while it was wider for conventional procedures (2.0–500 ng/mL). Moreover, repeatability (percentage relative standard deviation) was found to range between 5.6 and 10.4% (n = 3) for the continuous-flow procedure, with a better repeatability than that of conventional procedures (2.3–5.5% (n = 3)). Also, for the continuous-flow procedure, the estimated detection limit (signal-to-noise ratio = 3) was less than 2.4 ng/mL and extraction recoveries were within 8–10%, while the corresponding figures for conventional procedures were less than 0.6 ng/mL and 42–60%, respectively. Thus, the results showed that both continuous flow and conventional procedures were applicable for the extraction of model compounds. However, the conventional procedure was more convenient to use, and thus it was applied to determine sample drugs in real urine and wastewater samples.



Effect of fabrication strategy on the enantioseparation performance of β-cyclodextrin-functionalized polymethacrylate monoliths: A comparative evaluation

2017-08-28T04:51:19.404786-05:00

To evaluate the effect of the preparation strategy on the enantioseparation performance of β-cyclodextrin-functionalized monoliths, a series of β-cyclodextrin-functionalized organic polymeric monolithic columns were prepared through two-step, single-step, and one-pot approaches, using the same cyclodextrin, linker–spacer, and crosslinker. Physicochemical characterization of the columns was carried out by determining the morphology, β-cyclodextrin density, permeability, and chromatographic efficiency. For each type of monolithic column, the enantioresolution of 22 chiral compounds, including mandelic acid derivatives, nonsteroidal anti-inflammatory drugs, N-derivatized amino acids, and herbicides, was comparatively studied under optimum chromatographic conditions. The β-cyclodextrin-functionalized monolithic columns prepared through the one-pot approach exhibited higher enantioresolution for most chiral compounds, and they have the advantage of good controllability and simple preparation. On the other hand, the enantioresolution obtained on columns prepared through the single-step approach was quite unsatisfactory, and therefore the effect of using different linking spacers and crosslinkers was studied. A significant improvement of enantioresolution for 2-chloro-mandelic acid was obtained by using N,N-methylenebisacrylamide instead of ethylene dimethacrylate as the crosslinker in the single-step preparation.



A rapid method for the determination of brominated flame retardant concentrations in plastics and textiles entering the waste stream

2017-08-28T04:51:01.131585-05:00

Due to new European legislation, products going to waste are subject to ‘low persistent organic pollutant concentration limits’. Concentrations of restricted brominated flame retardants in waste products must be determined. A rapid extraction and clean-up method was developed for determination of brominated flame retardants in various plastics and textiles. The optimised method used vortexing and ultrasonication in dichloromethane followed by sulfuric acid clean-up to determine target compounds. Poly-brominated diphenyl ethers were determined by gas chromatography with mass spectrometry and hexabromocyclododecane by liquid chromatography with tandem mass spectrometry. Good recoveries of target analytes were obtained after three extraction cycles. The method was validated using poly-propylene and poly-ethylene certified reference materials as well as previously characterised textiles, expanded and extruded poly-styrene samples. Measured concentrations of target compounds showed good agreement with the certified values indicating good accuracy and precision. Clean extracts provided low noise levels resulting in low limits of quantification (0.8–1.5 ng/g for poly-brominated diphenyl ethers and 0.3 ng/g for α-, β- and γ-hexabromocyclododecane). The developed method was applied successfully to real consumer products entering the waste stream and it provided various advantages over traditional methods, including reduced analysis time, solvent consumption, minimal sample contamination and high sample throughput, which is crucial to comply with the implemented legislation.



Simultaneous detection of zinc dimethyldithiocarbamate and zinc ethylenebisdithiocarbamate in cabbage leaves by capillary electrophoresis with inductively coupled plasma mass spectrometry

2017-08-28T04:46:07.376611-05:00

We report a simple and highly sensitive method for the simultaneous detection of trace zinc dimethyldithiocarbamate and zinc ethylenebisdithiocarbamate by capillary electrophoresis with inductively coupled plasma mass spectrometry. Zinc dimethyldithiocarbamate and zinc ethylenebisdithiocarbamate were chelated with trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid to form a macromolecule complex. Then, these two compounds were separated by α-cyclodextrin-modified capillary electrophoresis within 12 min at a separation voltage of 15 kV and measured by inductively coupled plasma mass spectrometry. The developed method is sensitive with detection limit of 1.9 and 3.0 ng Zn/mL for zinc dimethyldithiocarbamate and zinc ethylenebisdithiocarbamate, respectively. By means of ultrasound-assisted extraction methods, zinc dimethyldithiocarbamate and zinc ethylenebisdithiocarbamate spiked into cabbage leaves were successfully extracted and determined with a relative standard deviation (n = 5) ≤ 6% and a recovery of 95–107%.



New approach applying a pet fish air pump in liquid-phase microextraction for the determination of Sudan dyes in food samples by HPLC

2017-08-28T04:46:00.422906-05:00

A new approach applying a pet fish air pump is introduced to develop an extraction method, namely, air-pump-enhanced emulsion, followed by salt-assisted emulsion breaking based on solidified floating organic drop microextraction for the extraction and preconcentration of Sudan I–IV before high-performance liquid chromatography. The applicability of this method was successfully demonstrated by determination of these dyes in four chili products that include chili powder, chili oil, chili sauce, and chili paste. An enrichment factor of 62 was obtained only with a sample solution of 5 mL. A linear range of 0.5–2500 ng/mL was obtained with a limit of detection of 0.16–0.24 ng/mL and recovery of 90–110%. This method is superior to other liquid–liquid extraction methods, as is simple, rapid, environmental friendly, and its phase separation needs no centrifugation. It also needs no disperser solvent and requires less organic solvent, and satisfies the criteria to be called as a green extraction. Therefore, this facile extraction method can be successfully applied in the determination of Sudan dyes in food samples.



Simultaneous quantification of volitinib and gefitinib in rat plasma by HPLC–MS/MS for application to a pharmacokinetic study in rats

2017-08-28T04:45:52.717022-05:00

A rapid, simple, and accurate procedure was developed and validated for the simultaneous quantification of two anticancer agents, volitinib and gefitinib in rat plasma by high-performance liquid chromatography with tandem mass spectrometry. The samples were separated by gradient elution from a cyano column within five minutes, using 0.1% formic acid in acetonitrile and 10 mM ammonium formate solution (pH 3.0) as mobile phase. When plasma samples were deproteinated by adding methanol, the analytes in the extract were detected in the positive ionization mode with the tracer ion mass of 346.1 145.1 for volitinib and 446.8 128.1 for gefitinib. The assay was determined to be valid in the concentration ranges of 2 to 1000 ng/mL for volitinib, and of 1 to 500 ng/mL for gefitinib. Intra- and interday accuracies ranged from 88.0 to 104.7% for volitinib and from 90.3 to 101%, for gefitinib. The precision of the assay ranged from 2.1 to 9.71% for volitinib and 2.31 to 12.1% for gefitinib. This method was successfully applied to a pharmacokinetic study of volitinib and gefitinib after the administration of an intravenous or oral dose, indicating that the developed assay can be used to simultaneously determine the concentrations of volitinib and gefitinib in rat plasma.



Direct online extraction and determination by supercritical fluid extraction with chromatography and mass spectrometry of targeted carotenoids from red Habanero peppers (Capsicum chinense Jacq.)

2017-08-28T04:45:46.797091-05:00

Recently, supercritical fluid chromatography coupled to mass spectrometry has gained attention as a fast and useful technology applied to the carotenoids analysis. However, no reports are available in the literature on the direct online extraction and determination by supercritical fluid extraction with chromatography and mass spectrometry. The aim of this research was the development of an online method coupling supercritical fluid extraction and supercritical fluid chromatography for a detailed targeted native carotenoids characterization in red habanero peppers. The online nature of the system, compared to offline approaches, improves run-to-run precision, enables the setting of batch-type applications, and reduces the risks of sample contamination. The extraction has been optimized using different temperatures, starting from 40°C up to 80°C. Multiple extractions, until depletion, were performed on the same sample to evaluate the extraction yield. The range of the first extraction yield, carried out at 80°C, which was the best extraction temperature, was 37.4–65.4%, with a %CV range of 2–12. Twenty-one targeted analytes were extracted and identified by the developed methodology in less than 17 min, including free, monoesters, and diesters carotenoids, in a very fast and efficient way. Quantification of the β-carotene was carried out by using the optimized conditions.



Quantitative studies of rhubarb using quantitative analysis of multicomponents by single marker and response surface methodology

2017-08-28T04:45:38.699431-05:00

In this work, we developed a novel approach to evaluate the contents of bioactive components in rhubarb. The present method was based on the quantitative analysis of multicomponents by a single-marker and response surface methodology approaches. The quantitative analysis of multicomponents by a single-marker method based on high-performance liquid chromatography coupled with photodiode array detection was developed and applied to determine the contents of 12 bioactive components in rhubarb. No significant differences were found in the results from the quantitative analysis of multicomponents by a single-marker and the external standard method. In order to maximize the extraction of 12 bioactive compounds in rhubarb, the ultrasonic-assisted extraction conditions were obtained by the response surface methodology coupled with Box–Behnken design. According to the obtained results, we showed that the optimal conditions would be as follows: proportion of ethanol/water 74.39%, solvent-to-solid ratio 24.07:1 v/w, extraction time 51.13 min, and extraction temperature 63.61°C. The analytical scheme established in this research should be a reliable, convenient, and appropriate method for quantitative determination of bioactive compounds in rhubarb.



Enantioseparation of pheniramine enantiomers by high-speed countercurrent chromatography using β-cyclodextrin derivatives as a chiral selector

2017-08-28T04:45:32.068642-05:00

The enantioselective separation of pheniramine was studied by a high-speed countercurrent chromatography method using β-cyclodextrin derivatives as a chiral selector. Several key variables, for instance, type of organic solvent and chiral selector, concentration of chiral selector, pH value of aqueous phase, and temperature on the enantioselectivity, were investigated systematically by liquid–liquid extraction experiments. Combining the results of extraction experiments and high-speed countercurrent chromatography, the most suitable conditions for separation of pheniramine enantiomers were obtained with the two-phase system that consisted of isobutyl acetate/aqueous phase, containing 0.02 mol/L carboxymethyl-β-cyclodextrin, pH 8.50 at 278.15 K. Under the optimal conditions, pheniramine enantiomer was successfully resolved after four cycles of high-speed countercurrent chromatography. By using high-performance liquid chromatography to analyze the fractions, the purities of both (+)-pheniramine and (–)-pheniramine were over 99% and the recovery of this method was up to 85–90%.



Vortex-assisted liquid–liquid microextraction of strontium from water samples using 4′,4″(5″)-di-(tert-butylcyclohexano)-18-crown-6 and tetraphenylborate

2017-08-28T04:45:24.04322-05:00

A vortex-assisted liquid–liquid microextraction method was developed for the chromatographic determination of strontium in aqueous samples. In the method, strontium was complexed with 4′,4″(5″)-di-(tert-butylcyclohexano)-18-crown-6 in the presence of tetraphenylborate as the counter anion, which increased the hydrophobicity of the ion-association complex, resulting in its improved extraction into 1-octanol. Strontium from the organic phase was stripped with nitric acid back to aqueous solution and determined by ion chromatography. The optimum microextraction conditions were as follows: 2.0 mL aqueous samples with 3 mM tetraphenylborate; 150 μL of 1-octanol as the extractant phase with 10 mM DtBuCH18C6; vortex extraction time for 10 s; centrifugation at 6000 rpm for 4 min; stripping by 0.1 M nitric acid. Under the optimum conditions, the detection limit for strontium was 0.005 mg/L. The calibration curves showed good linearity over the range between 0.01 and 2.5 mg/L. Intra- and interday precisions of the present method were satisfactory with relative standard deviations of 1.7 and 2.1%, respectively.



A new sample preparation and separation combination for the precise, accurate, and simultaneous determination of uracil and dihydrouracil in human plasma by reversed-phase HPLC

2017-08-14T05:45:22.319959-05:00

We have developed an efficient procedure and detection method using reversed-phase high-performance liquid chromatography for the simultaneous measurement of uracil and dihydrouracil in human plasma. The procedure, including chromatographic conditions and sample preparation, was optimized and validated. Optimization of the sample preparation included deproteinization, extraction, and cleanup. A new sample preparation method which resulted in an improved extraction yield of analytes and significantly reduced interference at low-wavelength UV detection was developed. The developed method was validated for specificity, linearity, limits of detection and quantitation, precision, and accuracy. All calibration curves showed excellent linear regression (R2 > 0.9990) within the testing range. The limit of detection for uracil and dihydrouracil was 2.5 and 5.0 ng/mL, respectively. The extraction yields were >94% for uracil and 91% for dihydrouracil. Intra- and interassay precision and accuracy for uracil and dihydrouracil were lower than 8% at all tested concentrations. The proposed method was successfully applied to measure plasma concentrations of uracil and dihydrouracil in colorectal cancer patients scheduled to receive fluoropyrimidine-based chemotherapy.



Recent applications of metal–organic frameworks in sample pretreatment

2017-07-20T07:25:42.391107-05:00

Metal–organic frameworks are promising materials in diverse analytical applications especially in sample pretreatment by virtue of their diverse structure topology, tunable pore size, permanent nanoscale porosity, high surface area, and good thermostability. According to hydrostability, metal–organic frameworks are divided into moisture-sensitive and water-stable types. In the actual applications, both kinds of metal–organic frameworks are usually engineered into hybrid composites containing magnetite, silicon dioxide, graphene, or directly carbonized to metal–organic frameworks derived carbon. These metal–organic frameworks based materials show good extraction performance to environmental pollutants. This review provides a critical overview of the applications of metal–organic frameworks and their composites in sample pretreatment modes, that is, solid-phase extraction, magnetic solid-phase extraction, micro-solid-phase extraction, solid-phase microextraction, and stir bar solid extraction.



Facile preparation of polydopamine-coated imprinted polymers on the surface of SiO2 for estrone capture in milk samples

2016-11-02T02:31:27.21102-05:00

Estrone molecularly imprinted polymers were synthesized through the self-polymerization of dopamine on the surface of silica gels, which had the characteristics of mild polymerization conditions, simple reaction procedure and good specific recognition ability for estrone. The estrone molecularly imprinted polymers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis and nitrogen adsorption–desorption tests. The characterization confirmed that the imprinted polymers were successfully grafted on the surface of silica gels. Through investigating the adsorption performance, the prepared estrone molecularly imprinted polymers exhibited high adsorption capacity, fast mass transfer, as well as excellent selectivity toward estrone. The estrone molecularly imprinted polymers as the solid-phase extraction adsorbent coupled with high-performance liquid chromatography was developed to determine estrone from the milk samples. The developed estrone molecularly imprinted polymer solid-phase extraction with high-performance liquid chromatography method exhibited satisfactory specificity, precision, accuracy and good linearity relationship in the range of 0.2–20 μg/mL. The developed method is simple, fast, effective and high specificity method and it provides a new method to detect the residues of estrone in animal foods.



Front Cover

2017-09-19T23:59:04.472297-05:00




Issue Information

2017-09-19T23:59:06.5931-05:00




Content: J. Sep. Science 18'17

2017-09-19T23:59:04.123718-05:00




Comparative analysis of 15 chemical constituents in Scutellaria baicalensis stem-leaf from different regions in China by ultra-high performance liquid chromatography with triple quadrupole tandem mass spectrometry

2017-08-14T01:01:48.355431-05:00

Scutellaria baicalensis is a traditional Chinese herbal medicine containing multiple components, which has been extensively used in clinics to treat epidemic febrile disease and hyperactivity cough. To get a deeper understanding about Scutellaria baicalensis stem-leaf resources, we analyzed 15 chemical constituents in 35 batches of Scutellaria baicalensis stem-leaf from eight regions in China. A rapid, simple, and sensitive method using ultra-high performance liquid chromatography coupled with triple quadrupole electrospray tandem mass spectrometry has been developed for the first time to simultaneously determine 15 chemical constituents (including phenolic acids and flavonoids) in Scutellaria baicalensis stem-leaf. Sufficient separation of 15 target constituents was achieved on a Waters Acquity UPLC BEH C18 (2.1 mm × 100 mm, 1.7 μm) column within 14 min under the optimized chromatographic conditions. The established method was validated and showed good linearity, precision, repeatability, stability, and recovery and was successfully applied for the simultaneous determination of the 15 chemical constituents in these samples. Hierarchical clustering analysis and principal components analysis were performed to estimate and classify these samples based on the contents of the 15 chemical constituents. This study provided theoretical basis and scientific evidence for the development and utilization of Scutellaria baicalensis stem-leaf resources.



Identification of metabolites in human and rat urine after oral administration of Xiao-Qing-Long-Tang granule using ultra high performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry

2017-08-14T05:42:15.198957-05:00

Xiao-Qing-Long-Tang is a traditional Chinese formula used for the treatment of cold syndrome, bronchitis, and nasal allergies for thousands of years. However, the in vivo integrated metabolism of its multiple components and the active chemical constituents of Xiao-Qing-Long-Tang remain unknown. In this study, a method using ultra high performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry was established for the detection and identification of the metabolites in human and rat urine after oral administration of Xiao-Qing-Long-Tang. A total of 19 compounds were detected or tentatively identified in human urine samples, including eight prototypes and 11 metabolites. Also, a total of 50 compounds were detected or tentatively identified in rat urine samples, including 15 prototypes and 35 metabolites detected with either a highly sensitive extracted ion chromatogram method or the MSE determination using Mass Fragment software. Our results indicated that phase Ⅱ reactions (e.g. glucuronidation and sulfation) were the main metabolic pathways of flavones, while phase I reactions (e.g. demethylation and hydroxylation) were the major metabolic reaction for alkaloids, lignans, and ginger essential oil. This investigation provided important structural information on the metabolism of Xiao-Qing-Long-Tang and provided evidence to obtain a more comprehensive metabolic profile.



Efficient separation of high-purity compounds from Oxytropis falcata using two-dimensional preparative chromatography

2017-08-28T04:51:29.482656-05:00

The separation of high-purity compounds from traditional Tibetan medicines plays an important role in investigating their bioactivity. Nevertheless, it is often quite difficult to isolate compounds with high purity because of the complexity of traditional Tibetan medicines. In this work, an offline two-dimensional reversed-phase preparative method was successfully developed for the separation of high-purity compounds from Oxytropis falcata. Based on the analysis results, an ODS C18 prep column was used for first-dimensional preparation, and 14.8 g of the crude sample was separated into five fractions with a recovery of 74.6%. Then, an XAqua C18 prep column was used to isolate high-purity compounds in the second-dimensional preparation because its separation selectivity is different with the ODS C18 stationary phase. As a result, eight compounds in the crude sample were isolated in more than 98% purity. This is the first report of trans-cinnamic acid (1) and trifolirhizin (2) from Oxytropis falcata. This method has the potential to be an efficient separation method of high-purity compounds from Oxytropis falcata and it shows great promise for the separation of high-purity compounds from complex samples.



Response surface methodology based on central composite design accompanied by multivariate curve resolution to model gradient hydrophilic interaction liquid chromatography: Prediction of separation for five major opium alkaloids

2017-08-28T04:51:44.977022-05:00

Hydrophilic interaction liquid chromatography on bare silica presents some benefits for analysis and purification of ionizable basic alkaloids. This mode was used to separate five major opium alkaloids: morphine, codeine, thebaine, papaverine, and noscapine. Central composite design based on response surface methodology was applied for experimental design, modeling, and optimization in a single-step gradient method. The main effects and their interactions (initial percentage of modifier, changing range of modifier in run time, pH of buffer, and its concentration) were investigated in 30 experiments. Multivariate curve resolution-alternating least squares, by resolving overlapped curves, helped in the accurate calculation of baseline resolution factors to be modeled and optimized more accurately. Then three crucial resolution factors besides elution time were modeled in quadratic and cubic equations and optimized. In addition to the four factors, five extra logarithmic, and nonlogarithmic factors extracted from the four factors to give nine factors overall were inspected on mechanism of retention. It was shown that a linear combination consist of four independence variables successfully describes morphinans retentivity in a single-step gradient method.



Optimizing gradient conditions in online comprehensive two-dimensional reversed-phase liquid chromatography by use of the linear solvent strength model

2017-09-04T08:26:23.469946-05:00

The linear solvent strength model was used to predict coverage in online comprehensive two-dimensional reversed-phase liquid chromatography. The prediction model uses a parallelogram to describe the separation space covered with peaks in a system with limited orthogonality. The corners of the parallelogram are assumed to behave like chromatographic peaks and the position of these pseudo-compounds was predicted. A mix of 25 polycyclic aromatic compounds were used as a test. The precision of the prediction, span 0–25, was tested by varying input parameters, and was found to be acceptable with root mean square errors of 3. The accuracy of the prediction was assessed by comparing with the experimental coverages. Less than half of experimental coverages were outside prediction ± 1 × root mean square error and none outside prediction ± 2 × root mean square error. Accuracy was lower when retention factors were low, or when gradient conditions affected parameters not included in the model, e.g. second dimension gradient time affects the second dimension equilibration time. The concept shows promise as a tool for gradient optimization in online comprehensive two-dimensional liquid chromatography, as it mitigates the tedious registration and modeling of all sample constituents, a circumstance that is particularly appealing when dealing with complex samples.



Determination of seven drugs of abuse and their metabolites in surface and wastewater using solid-phase extraction coupled to liquid chromatography with high-resolution mass spectrometry

2017-08-14T05:40:59.219818-05:00

A method based on liquid chromatography with electrospray ionization high-resolution mass spectrometry (Exactive Orbitrap) combined with solid-phase extraction using a strong cationic exchange mixed-mode sorbent has been developed for the determination of seven drugs of abuse, including two synthetic cathinones, as well as some of their metabolites in environmental water samples. The method provides low detection limits and a high confirmation power thanks to the diagnostic and two fragment ions monitored for each compound in high-resolution mass spectrometry, providing six identification points for each analyte. The clean-up step based on methanol in the extraction step adequately decreased the matrix effect, mainly for river and effluent water, and provided suitable process efficiency. Method detection and quantitation limits for environmental waters were at low nanogram per liter. The method was applied to analyze the samples of influent and effluent wastewater, as well as surface water. Codeine, methadone, and its metabolite were determined in all samples of wastewater and the metabolite of cocaine, benzoylecgonine, was found at the highest concentration.



Modeling of bispecific antibody elution in mixed-mode cation-exchange chromatography

2017-08-14T05:41:33.243325-05:00

The increasing demand for cost-efficient manufacturing of biopharmaceuticals has been the main driving force for the development of novel chromatography resins, which resulted in the development of multimodal or mixed-mode chromatographic resins. Most of them combine electrostatic and hydrophobic functionalities and are designed to deliver unique selectivity and increased binding capacities also at increased ionic strength. However, the mechanism of the protein–resin interaction in mixed-mode chromatography is still not fully understood. The performance of protein separations in mixed-mode chromatography is consequently difficult to predict. In this work, we present a model combining both salt and pH dependence to characterize and to predict protein retention in mixed-mode chromatography. The model parameters are determined based on simple linear pH gradient elution experiments at different ionic strengths and they are directly transferable for the prediction of salt-induced elution at fixed pH. Validity of the model is demonstrated for a bispecific antibody and its product-related impurities.



Green micellar HPLC analysis of three angiotensin-converting enzyme inhibitors in their mixtures with hydrochlorothiazide and modeling of their retention behavior by fitting to Foley's model

2017-08-28T04:51:06.128179-05:00

We present an environmentally friendly method for the analysis of three angiotensin-converting enzyme inhibitors and hydrochlorothiazide simultaneously using a green micellar eluent for the first time. The chromatographic separation of enalapril maleate, lisinopril dihydrate, benazepril hydrochloride, and hydrochlorothiazide was implemented on an octadecyl silica column with a solution containing sodium dodecyl sulfate (0.12 M), 1-propyl alcohol (10% v/v), triethylamine (0.3% v/v), and H3PO4 (0.02 M) at pH 3.6 as the mobile phase and UV detection at 210 nm. Validity of the method was confirmed and it exhibited good linearity within the ranges of 5.0–50.0 μg/mL for hydrochlorothiazide and 10.0–60.0 μg/mL for the three angiotensin-converting enzyme inhibitors with a limit of detection of 0.39 to 1.15 μg/mL for all the studied drugs. The developed micellar high-performance liquid chromatography method enables the quantification of the targeted angiotensin-converting enzyme inhibitors in combined tablets with hydrochlorothiazide by isocratic elution. There is no need for special precautions to prevent broadening and splitting of their chromatographic peaks. The method fulfills the society rights for safe and green analytical methods. The retention behavior of the four studied drugs was fitted to Foley's model and their association equilibria to the micelles ([...]