Determination of trace polychlorinated biphenyls and organochlorine pesticides in water samples through large-volume stir bar sorptive extraction method with thermal desorption gas chromatography

A fast and sensitive analytical method based on stir bar sorptive extraction technology with gas chromatography and mass spectrometry was developed to simultaneously analyze 18 kinds of polychlorinated biphenyls and 20 kinds of organochlorine pesticides in aqueous samples. A long adsorption time and small sample volume, which are problems encountered in conventional methods of stir bar sorptive extraction, were effectively solved by simultaneously using multiple stir bars for enrichment with sequential cryofocusing and merged injection. Optimized results showed good linear coefficients in the range of 10–500 ng/L and the method detection limits of 0.12–2.07 ng/L for polychlorinated biphenyls and organochlorine pesticides. The recovery ratios of the spiked samples at different concentrations were between 64.7 and 111.0%, and their relative standard deviations ranged from 0.9 to 17.6%. Four types of the studied compounds were determined in Qiantang River water samples, and their contents were between 0.82 and 5.00 ng/L.

Abstract

A fast and sensitive analytical method based on stir bar sorptive extraction technology with gas chromatography and mass spectrometry was developed to simultaneously analyze 18 kinds of polychlorinated biphenyls and 20 kinds of organochlorine pesticides in aqueous samples. A long adsorption time and small sample volume, which are problems encountered in conventional methods of stir bar sorptive extraction, were effectively solved by simultaneously using multiple stir bars for enrichment with sequential cryofocusing and merged injection. Optimized results showed good linear coefficients in the range of 10–500 ng/L and the method detection limits of 0.12–2.07 ng/L for polychlorinated biphenyls and organochlorine pesticides. The recovery ratios of the spiked samples at different concentrations were between 64.7 and 111.0%, and their relative standard deviations ranged from 0.9 to 17.6%. Four types of the studied compounds were determined in Qiantang River water samples, and their contents were between 0.82 and 5.00 ng/L.

Determination of the transformation of ginsenosides in Ginseng Radix et Rhizoma during decoction with water using ultra-fast liquid chromatography coupled with tandem mass spectrometry

This study was conducted to determine the variations of ginsenosides in Ginseng Radix et Rhizoma when using different preparation solvents, and explore the major factors for changes. With an established ultra-fast liquid chromatography coupled with tandem mass spectrometry method which could quantify 52 ginsenosides, the extraction differences were characterized and compared using different solvents (water, 70% aqueous ethanol and ethanol). Subsequently, a series of aqueous solutions with different pH were prepared to test the influence of pH to the changes of ginsenosides. Meanwhile, acetic acid and aspartic acid were used to verify whether the reaction had a relationship with the kind of acids. After refluxing with water, not only highly polar ginsenosides were extracted, some less polar ginsenosides such as ginsenoside Rg3, Rg5, Rk1 and Rh2 occurred or increased rapidly. Further experiments indicated that less polar ginsenosides were easier to generate at low pH values, and the reaction was only related to pH other than what kind of acids. It is the first time to elaborate the contents variation of 52 ginsenosides when using different extraction methods. The results indicated decoction with water could enhance the transformation of highly polar ginsenosides to less polar ginsenosides and the process was pH dependent.
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Abstract

This study was conducted to determine the variations of ginsenosides in Ginseng Radix et Rhizoma when using different preparation solvents, and explore the major factors for changes. With an established ultra-fast liquid chromatography coupled with tandem mass spectrometry method which could quantify 52 ginsenosides, the extraction differences were characterized and compared using different solvents (water, 70% aqueous ethanol and ethanol). Subsequently, a series of aqueous solutions with different pH were prepared to test the influence of pH to the changes of ginsenosides. Meanwhile, acetic acid and aspartic acid were used to verify whether the reaction had a relationship with the kind of acids. After refluxing with water, not only highly polar ginsenosides were extracted, some less polar ginsenosides such as ginsenoside Rg3, Rg5, Rk1 and Rh2 occurred or increased rapidly. Further experiments indicated that less polar ginsenosides were easier to generate at low pH values, and the reaction was only related to pH other than what kind of acids. It is the first time to elaborate the contents variation of 52 ginsenosides when using different extraction methods. The results indicated decoction with water could enhance the transformation of highly polar ginsenosides to less polar ginsenosides and the process was pH dependent.

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Chiral separation of disease biomarkers with 2-hydroxycarboxylic acid structure#

Chiral 2-hydroxycarboxylic acids are compounds that have been linked to particular diseases and are putative biomarkers with some diagnostic potential. The importance of identifying whether a particular enantiomer is related to certain diseases has been encouraged recently. However, in many cases it has not yet been elucidated whether there are stereochemical implications with respect to these biomarkers and whether their enantioselective analysis provides new insights and diagnostic potential. In this study 13 disease-related chiral 2-hydrocarboxylic acids were studied for their chiral separation by high-performance liquid chromatography on three cinchona alkaloid-derived chiral stationary phases. From a subgroup of eight 2-hydroxymonocarboxylic acids, baseline resolution could be achieved and inversion of elution order by exchanging tert-butylcarbamoyl quinidine chiral stationary phase (Chiralpak QD-AX) for the corresponding quinine analogue (Chiralpak QN-AX) is shown for seven of them. Furthermore, conditions for chiral separation of the 2-hydroxydicarboxylic acids, citramalic acid, 2-isopropylmalic acid and 2-hydroxyadipic acid are reported and compared to the previous reported conditions for 2-hydroxyglutaric acid and malic acid.
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Abstract

Chiral 2-hydroxycarboxylic acids are compounds that have been linked to particular diseases and are putative biomarkers with some diagnostic potential. The importance of identifying whether a particular enantiomer is related to certain diseases has been encouraged recently. However, in many cases it has not yet been elucidated whether there are stereochemical implications with respect to these biomarkers and whether their enantioselective analysis provides new insights and diagnostic potential. In this study 13 disease-related chiral 2-hydrocarboxylic acids were studied for their chiral separation by high-performance liquid chromatography on three cinchona alkaloid-derived chiral stationary phases. From a subgroup of eight 2-hydroxymonocarboxylic acids, baseline resolution could be achieved and inversion of elution order by exchanging tert-butylcarbamoyl quinidine chiral stationary phase (Chiralpak QD-AX) for the corresponding quinine analogue (Chiralpak QN-AX) is shown for seven of them. Furthermore, conditions for chiral separation of the 2-hydroxydicarboxylic acids, citramalic acid, 2-isopropylmalic acid and 2-hydroxyadipic acid are reported and compared to the previous reported conditions for 2-hydroxyglutaric acid and malic acid.

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A simple approach to prepare a sulfone-embedded stationary phase for HPLC

In the present study, a polar-embedded reversed-phase liquid chromatographic stationary phase which contained internal sulfone groups was prepared. The synthesis involved the “thiol-ene” click chemistry between the vinyl functionalized silica and 1-octadecanethiol, followed by the oxidization of sulfide to sulfone groups. The resulting material simultaneously possessed the alkyl chain, i.e. C18, and the internal sulfone groups. Elemental analysis demonstrates that the element contents of the C18/sulfone silica were C 8.94%, H 1.87% and S 0.66%. Chromatographic evaluations indicate that the C18/sulfone stationary phase exhibited a little less retention than the C18/sulfide one. A comparable chromatographic performance of neutral analytes was obtained on these two columns, but much better chromatographic performance in the case of basic and acid analytes was obtained on C18/sulfone stationary phase with additional features such as lower silanol activity, better stability (stable working conditions of pH 1.0–10.0) and better compatibility with 100% aqueous mobile phases. The batch-to-batch reproducibility was acceptable (the RSDs of retention times for the probes were no higher than 1.73%), demonstrating the suitability of the applied synthetic strategy for the new stationary phase. The C18/sulfone is a promising polar-embedded RPLC stationary phase.
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Abstract

In the present study, a polar-embedded reversed-phase liquid chromatographic stationary phase which contained internal sulfone groups was prepared. The synthesis involved the “thiol-ene” click chemistry between the vinyl functionalized silica and 1-octadecanethiol, followed by the oxidization of sulfide to sulfone groups. The resulting material simultaneously possessed the alkyl chain, i.e. C18, and the internal sulfone groups. Elemental analysis demonstrates that the element contents of the C18/sulfone silica were C 8.94%, H 1.87% and S 0.66%. Chromatographic evaluations indicate that the C18/sulfone stationary phase exhibited a little less retention than the C18/sulfide one. A comparable chromatographic performance of neutral analytes was obtained on these two columns, but much better chromatographic performance in the case of basic and acid analytes was obtained on C18/sulfone stationary phase with additional features such as lower silanol activity, better stability (stable working conditions of pH 1.0–10.0) and better compatibility with 100% aqueous mobile phases. The batch-to-batch reproducibility was acceptable (the RSDs of retention times for the probes were no higher than 1.73%), demonstrating the suitability of the applied synthetic strategy for the new stationary phase. The C18/sulfone is a promising polar-embedded RPLC stationary phase.

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Headspace solid-phase microextraction and gas chromatographic analysis of low-molecular-weight sulfur volatiles with pulsed flame photometric detection and quantification by a stable isotope dilution assay

Low-molecular-weight volatile sulfur compounds such as thiols, sulfides, disulfides as well as thioacetates cause a sulfidic off-flavor in wines even at low concentration levels. The proposed analytical method for quantification of these compounds in wine is based on headspace solid-phase microextraction, followed by gas chromatographic analysis with sulfur-specific detection using a pulsed flame photometric detector. Robust quantification was achieved via a stable isotope dilution assay using commercial and synthesized deuterated isotopic standards. The necessary chromatographic separation of analytes and isotopic standards benefits from the inverse isotope effect realized on an apolar polydimethylsiloxane stationary phase of increased film thickness. Interferences with sulfur-specific detection in wine caused by sulfur dioxide were minimized by addition of propanal. The method provides adequate validation data, with good repeatability and limits of detection and quantification. It suits the requirements of wine quality management, allowing the control of oenological treatments to counteract an eventual formation of excessively high concentration of such malodorous compounds.
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Abstract

Low-molecular-weight volatile sulfur compounds such as thiols, sulfides, disulfides as well as thioacetates cause a sulfidic off-flavor in wines even at low concentration levels. The proposed analytical method for quantification of these compounds in wine is based on headspace solid-phase microextraction, followed by gas chromatographic analysis with sulfur-specific detection using a pulsed flame photometric detector. Robust quantification was achieved via a stable isotope dilution assay using commercial and synthesized deuterated isotopic standards. The necessary chromatographic separation of analytes and isotopic standards benefits from the inverse isotope effect realized on an apolar polydimethylsiloxane stationary phase of increased film thickness. Interferences with sulfur-specific detection in wine caused by sulfur dioxide were minimized by addition of propanal. The method provides adequate validation data, with good repeatability and limits of detection and quantification. It suits the requirements of wine quality management, allowing the control of oenological treatments to counteract an eventual formation of excessively high concentration of such malodorous compounds.

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Enhanced headspace single drop microextraction method using deep eutectic solvent based magnetic bucky gels: Application to the determination of volatile aromatic hydrocarbons in water and urine samples

A facile headspace single drop microextraction method was developed using deep eutectic solvent based magnetic bucky gel as the extraction solvent for the first time. The hydrophobic magnetic bucky gel was formed by combining choline chloride/chlorophenol deep eutectic solvent and magnetic multi-walled carbon nanotube nanocomposite. Magnetic susceptibility, high viscosity, high sorbing ability and tunable extractability of organic analytes are the desirable advantages of the prepared gel. Using rod magnet as suspensor in combination with the magnetic susceptibility of the prepared gel resulted in a highly stable droplet. This stable droplet eliminated the possibility of drop dislodgement. The prepared droplet made it possible to complete the extraction process in high temperatures and elevated agitation rates. Furthermore, using larger micro-droplet volumes without any operational problems became possible. These facts resulted in shorter sample preparation time, higher sensitivity of the method and lower detection limits. Under the optimized conditions, an enrichment factor of 520–587, limit of detection of 0.05–0.90 ng/mL, and linearity range of 0.2–2000 ng/mL (coefficient of determination = 0.9982–0.9995) were obtained. Relative standard deviations were < 10%. This method was successfully coupled with gas chromatography and used for the determination of benzene, toluene, ethylbenzene and xylene isomers as harmful volatile organic compounds in water and urine samples.
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Abstract

A facile headspace single drop microextraction method was developed using deep eutectic solvent based magnetic bucky gel as the extraction solvent for the first time. The hydrophobic magnetic bucky gel was formed by combining choline chloride/chlorophenol deep eutectic solvent and magnetic multi-walled carbon nanotube nanocomposite. Magnetic susceptibility, high viscosity, high sorbing ability and tunable extractability of organic analytes are the desirable advantages of the prepared gel. Using rod magnet as suspensor in combination with the magnetic susceptibility of the prepared gel resulted in a highly stable droplet. This stable droplet eliminated the possibility of drop dislodgement. The prepared droplet made it possible to complete the extraction process in high temperatures and elevated agitation rates. Furthermore, using larger micro-droplet volumes without any operational problems became possible. These facts resulted in shorter sample preparation time, higher sensitivity of the method and lower detection limits. Under the optimized conditions, an enrichment factor of 520–587, limit of detection of 0.05–0.90 ng/mL, and linearity range of 0.2–2000 ng/mL (coefficient of determination = 0.9982–0.9995) were obtained. Relative standard deviations were < 10%. This method was successfully coupled with gas chromatography and used for the determination of benzene, toluene, ethylbenzene and xylene isomers as harmful volatile organic compounds in water and urine samples.

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Simple and accurate method for determining dissolved inorganic carbon in environmental water by reaction headspace gas chromatography

We investigate a simple and accurate method for quantitatively analyzing dissolved inorganic carbon in environmental water by reaction headspace gas chromatography. The neutralization reaction between the inorganic carbon species (i.e., bicarbonate ions and carbonate ions) in environmental water and hydrochloric acid is carried out in a sealed headspace vial, and the carbon dioxide formed from the neutralization reaction, the self-decomposition of carbonic acid and dissolved carbon dioxide in environmental water is then analyzed by headspace gas chromatography. The data show that the headspace gas chromatography method has good precision (relative standard deviation ≤ 1.63%) and accuracy (relative differences ≤ 5.81% compared with the coulometric titration technique). The headspace gas chromatography method is simple, reliable and can be well applied in the dissolved inorganic carbon detection in environmental water.
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Abstract

We investigate a simple and accurate method for quantitatively analyzing dissolved inorganic carbon in environmental water by reaction headspace gas chromatography. The neutralization reaction between the inorganic carbon species (i.e., bicarbonate ions and carbonate ions) in environmental water and hydrochloric acid is carried out in a sealed headspace vial, and the carbon dioxide formed from the neutralization reaction, the self-decomposition of carbonic acid and dissolved carbon dioxide in environmental water is then analyzed by headspace gas chromatography. The data show that the headspace gas chromatography method has good precision (relative standard deviation ≤ 1.63%) and accuracy (relative differences ≤ 5.81% compared with the coulometric titration technique). The headspace gas chromatography method is simple, reliable and can be well applied in the dissolved inorganic carbon detection in environmental water.

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Separation and determination of polyurethane amine catalysts in polyether polyols by using UHPLC–Q-TOF-MS on a reversed-phase/cation-exchange mixed-mode column

A simple, selective and accurate ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was established and validated for the efficient separation and quantification of polyurethane amine catalysts in polyether polyols. Amine catalysts were primarily separated in polyether polyol-based sample by solid-phase extraction, and further baseline separated on a reversed-phase/cation-exchange mixed-mode column (SiELC Primesep™ 200) using 0.1% trifluoroacetic acid/acetonitrile as a mobile phase in gradient elution mode at a flow rate of 0.2 mL/min. High-resolution quadrupole time-of-flight mass spectrometry analysis in electrospray ionization positive mode allowed the identification as N,N′-bis[3-(dimethylamino)propyl]urea, N-[2-(2-dimethylaminoethoxy)ethyl]-N-methyl-1,3-propanediamine and N,N,N′,N′-tetramethyldipropylenetriamine. The method was validated and presented good linearity for all the analytes in blank matrices within the concentration range of 0.20–5.0 or 0.1–2.0 μg/mL with the correlation coefficients (R2) ranging from 0.986 to 0.997. Method recovery ranged within 81–105% at all three levels (80, 100 and 120% of the original amount) with relative standard deviations of 1.0–6.2%. The limits of detection were in the range of 0.007–0.051 μg/mL. Good precision was obtained with relative standard deviation below 3.2 and 0.72% for peak area and retention time of three amines, respectively.
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Abstract

A simple, selective and accurate ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry method was established and validated for the efficient separation and quantification of polyurethane amine catalysts in polyether polyols. Amine catalysts were primarily separated in polyether polyol-based sample by solid-phase extraction, and further baseline separated on a reversed-phase/cation-exchange mixed-mode column (SiELC Primesep 200) using 0.1% trifluoroacetic acid/acetonitrile as a mobile phase in gradient elution mode at a flow rate of 0.2 mL/min. High-resolution quadrupole time-of-flight mass spectrometry analysis in electrospray ionization positive mode allowed the identification as N,N′-bis[3-(dimethylamino)propyl]urea, N-[2-(2-dimethylaminoethoxy)ethyl]-N-methyl-1,3-propanediamine and N,N,N′,N′-tetramethyldipropylenetriamine. The method was validated and presented good linearity for all the analytes in blank matrices within the concentration range of 0.20–5.0 or 0.1–2.0 μg/mL with the correlation coefficients (R2) ranging from 0.986 to 0.997. Method recovery ranged within 81–105% at all three levels (80, 100 and 120% of the original amount) with relative standard deviations of 1.0–6.2%. The limits of detection were in the range of 0.007–0.051 μg/mL. Good precision was obtained with relative standard deviation below 3.2 and 0.72% for peak area and retention time of three amines, respectively.

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Isolation and purification of food-grade C-phycocyanin from Arthrospira platensis and its determination in confectionery by HPLC with Diode Array Detection

C-Phycocyanin is the major phycobiliprotein in Arthrospira platensis, also known as Spirulina, which is a cyanobacterium used as a dietary supplement because of its powerful effects on body and brain. C-phycocyanin is a blue-colored accessory photosynthetic pigment with multiple applications in food industry as natural dye or additive, and in pharmaceuticals. This study presents a simple protocol for the extraction and purification of food-grade C-phycocyanin from Arthrospira platensis. The cell lysis of cyanobacterium was performed by sonication combined with repeated freezing and thawing cycles. The purification of the crude extract of C-phycocyanin was carried out by ammonium sulfate precipitation followed by ion exchange chromatography resulting in 2.5 purity. The purity of phycocyanobilin chromophore has been tested by UV-visible spectrophotometry by monitoring the absorption after each stage of purification. An high-performance liquid chromatography method has been developed and validated for the determination of food-grade C-phycocyanin. Intra-day and inter-day precision values less than 5.6% and recovery greater than 91.2% indicated high precision and accuracy of the method for analysis of C-phycocyanin. The method has been applied to commercial confectionery of blue color and to the purified protein obtained in the first stage of the study.
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Abstract

C-Phycocyanin is the major phycobiliprotein in Arthrospira platensis, also known as Spirulina, which is a cyanobacterium used as a dietary supplement because of its powerful effects on body and brain. C-phycocyanin is a blue-colored accessory photosynthetic pigment with multiple applications in food industry as natural dye or additive, and in pharmaceuticals. This study presents a simple protocol for the extraction and purification of food-grade C-phycocyanin from Arthrospira platensis. The cell lysis of cyanobacterium was performed by sonication combined with repeated freezing and thawing cycles. The purification of the crude extract of C-phycocyanin was carried out by ammonium sulfate precipitation followed by ion exchange chromatography resulting in 2.5 purity. The purity of phycocyanobilin chromophore has been tested by UV-visible spectrophotometry by monitoring the absorption after each stage of purification. An high-performance liquid chromatography method has been developed and validated for the determination of food-grade C-phycocyanin. Intra-day and inter-day precision values less than 5.6% and recovery greater than 91.2% indicated high precision and accuracy of the method for analysis of C-phycocyanin. The method has been applied to commercial confectionery of blue color and to the purified protein obtained in the first stage of the study.

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Application of ionic liquid magnetized stirring bar liquid-phase microextraction coupled with HPLC for the determination of naphthoquinones in Zicao

In this paper, a green, rapid and simple method, ionic liquid-magnetized stirring bar liquid-phase microextraction was developed for the determination of naphthoquinones, including shikonin and β,β’-dimethylacrylshikonin, in Zicao. This method permits active magnetic stirring, extraction and pre-enrichment in a single device simultaneously, so the extract is conveniently collected. The analytes were extracted from the sample to ionic liquid-magnetized stirring bar, then the analyte-adsorbed magnetized stirring bar can be readily isolated from the sample solution by a magnet. The key experimental parameters were investigated and optimized, including the type and volume of ionic liquid, extraction time, salt concentration, stirring speed and pH. The recoveries were in the range of 89.47–102.38%, and good reproducibilities were obtained with relative standard deviation below 5.36%. Compared with the conventional extraction methods, the proposed method is quicker and more effective.
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Abstract

In this paper, a green, rapid and simple method, ionic liquid-magnetized stirring bar liquid-phase microextraction was developed for the determination of naphthoquinones, including shikonin and β,β’-dimethylacrylshikonin, in Zicao. This method permits active magnetic stirring, extraction and pre-enrichment in a single device simultaneously, so the extract is conveniently collected. The analytes were extracted from the sample to ionic liquid-magnetized stirring bar, then the analyte-adsorbed magnetized stirring bar can be readily isolated from the sample solution by a magnet. The key experimental parameters were investigated and optimized, including the type and volume of ionic liquid, extraction time, salt concentration, stirring speed and pH. The recoveries were in the range of 89.47–102.38%, and good reproducibilities were obtained with relative standard deviation below 5.36%. Compared with the conventional extraction methods, the proposed method is quicker and more effective.

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Temperature-programmed multi-capillary gas chromatograph microcolumn for the analysis of odorous sulfur pollutants

We report the fabrication and performance of a silicon-on-glass micro gas chromatography eight-capillary column based on micro-electromechanical systems technology which is 50 cm long, 30 μm wide and 300 μm deep. According to the theory of a gas chromatography column, an even gas flow among different capillaries play a vital role in the peak broadening. Thus, a flow splitter structure is designed by the finite element method through the comparison of the velocity distributions of the eight-capillary columns with and without splitter as well as an open tubular column. The simulation results reveal that eight-capillary column with flow splitters can receive more uniform flow velocity in different capillaries, hence decreases the peak broadening and in turn increases the separation efficiency. The separation experiment results show that the separation efficiency of about 22 000 plates/m is achieved with the chip column temperature-programmed for analysis of odorous sulfur pollutants. This figure is nearly two times higher than that of the commercial capillary column coated the similar stationary phase. And the separation time of all the components in the microcolumn is less than 3.8 min, which is faster than the commercial capillary column.
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Abstract

We report the fabrication and performance of a silicon-on-glass micro gas chromatography eight-capillary column based on micro-electromechanical systems technology which is 50 cm long, 30 μm wide and 300 μm deep. According to the theory of a gas chromatography column, an even gas flow among different capillaries play a vital role in the peak broadening. Thus, a flow splitter structure is designed by the finite element method through the comparison of the velocity distributions of the eight-capillary columns with and without splitter as well as an open tubular column. The simulation results reveal that eight-capillary column with flow splitters can receive more uniform flow velocity in different capillaries, hence decreases the peak broadening and in turn increases the separation efficiency. The separation experiment results show that the separation efficiency of about 22 000 plates/m is achieved with the chip column temperature-programmed for analysis of odorous sulfur pollutants. This figure is nearly two times higher than that of the commercial capillary column coated the similar stationary phase. And the separation time of all the components in the microcolumn is less than 3.8 min, which is faster than the commercial capillary column.

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Geographic impact evaluation of the quality of Alismatis Rhizoma by untargeted metabolomics and quantitative assay

The geographic impact on the quality of Alismatis Rhizoma (derived from the tuber of Alisma orientale), a reputable diuretic traditional Chinese medicine, has seldom been evaluated. Here a metabolomics-driven approach targeting the bioactive protostane triterpenes was developed, by incorporating ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry based untargeted metabolite profiling and multiple reaction monitoring quantitative assay, to probe the triterpene differences between Alismatis Rhizoma samples collected from Sichuan, Fujian, and Jiangxi Provinces. Following the metabolomics workflows, the samples from Sichuan and Jiangxi displayed distinct differences in their triterpene profiles, while those from Fujian showed remarkable intra-class variation. Twenty-three triterpenes were identified to contribute most to the differentiated clustering. A sensitive, precise, repeatable, and accurate quantitative assay method was established on a hybrid triple quadrupole-linear ion trap mass spectrometer to quantify the contents of eight triterpene compounds. Taking into account the metabolomics and quantitation results, alisol B 23-acetate and alisol A are significantly different in Alismatis Rhizoma from Sichuan and Jiangxi Provinces, and they may have the potential for geographic discrimination. These results illustrate how geographic difference impact the triterpene chemistry of Alismatis Rhizoma. Metabolomics-driven chemical comparison is suitable for the quality evaluation of traditional Chinese medicine.
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Abstract

The geographic impact on the quality of Alismatis Rhizoma (derived from the tuber of Alisma orientale), a reputable diuretic traditional Chinese medicine, has seldom been evaluated. Here a metabolomics-driven approach targeting the bioactive protostane triterpenes was developed, by incorporating ultra high performance liquid chromatography with quadrupole time-of-flight mass spectrometry based untargeted metabolite profiling and multiple reaction monitoring quantitative assay, to probe the triterpene differences between Alismatis Rhizoma samples collected from Sichuan, Fujian, and Jiangxi Provinces. Following the metabolomics workflows, the samples from Sichuan and Jiangxi displayed distinct differences in their triterpene profiles, while those from Fujian showed remarkable intra-class variation. Twenty-three triterpenes were identified to contribute most to the differentiated clustering. A sensitive, precise, repeatable, and accurate quantitative assay method was established on a hybrid triple quadrupole-linear ion trap mass spectrometer to quantify the contents of eight triterpene compounds. Taking into account the metabolomics and quantitation results, alisol B 23-acetate and alisol A are significantly different in Alismatis Rhizoma from Sichuan and Jiangxi Provinces, and they may have the potential for geographic discrimination. These results illustrate how geographic difference impact the triterpene chemistry of Alismatis Rhizoma. Metabolomics-driven chemical comparison is suitable for the quality evaluation of traditional Chinese medicine.

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Simultaneous quantitative assessment of nine glycosides in tobacco by LC–MS/MS

A simple and efficient method combining ultrasound-assisted extraction, the conditions of which were optimized by response surface methodology, with liquid chromatography and tandem mass spectrometry was established and validated for the absolute quantification of nine non-volatile neutral glycosides originating from tobacco (Nicotiana tobaccum L.) leaves, comprising three phenolic glycosides, one benzanoid glycoside and five sesquiterpene glycosides within three isomers, originating from tobacco leaves. Factors of extraction time, sample quantity, extraction solvent, liquid chromatographic conditions and electrospray ionization parameters were carefully investigated to ensure the selectivity and sensitivity of the method. All calibration curves showed excellent coefficients of determination ranging from 0.9940 to 0.9996, within the range of tested concentrations. The limits of detection and quantification were 2.33–25.9 and 7.06–78.5 ng/mL, respectively. Satisfactory values of accuracy were between 80.1 to 107.9% among different sample matrixes. The relative standard deviations of intra- and inter-day analysis were less than 13.7 and 13.0% respectively. The developed method was successfully applied in a pilot study to determine the amounts of the nine endogenous glycosides in real flue-cured tobacco samples obtained from different habitats in China.
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Abstract

A simple and efficient method combining ultrasound-assisted extraction, the conditions of which were optimized by response surface methodology, with liquid chromatography and tandem mass spectrometry was established and validated for the absolute quantification of nine non-volatile neutral glycosides originating from tobacco (Nicotiana tobaccum L.) leaves, comprising three phenolic glycosides, one benzanoid glycoside and five sesquiterpene glycosides within three isomers, originating from tobacco leaves. Factors of extraction time, sample quantity, extraction solvent, liquid chromatographic conditions and electrospray ionization parameters were carefully investigated to ensure the selectivity and sensitivity of the method. All calibration curves showed excellent coefficients of determination ranging from 0.9940 to 0.9996, within the range of tested concentrations. The limits of detection and quantification were 2.33–25.9 and 7.06–78.5 ng/mL, respectively. Satisfactory values of accuracy were between 80.1 to 107.9% among different sample matrixes. The relative standard deviations of intra- and inter-day analysis were less than 13.7 and 13.0% respectively. The developed method was successfully applied in a pilot study to determine the amounts of the nine endogenous glycosides in real flue-cured tobacco samples obtained from different habitats in China.

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Immobilized-enzyme reactors integrated with capillary electrophoresis for pharmaceutical research

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

Abstract

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

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

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

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

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

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

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

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

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

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

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

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

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

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Rapid and green determination of 58 fragrance allergens in plush toys

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

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

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

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

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

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