A sensitive LC–MS/MS method for simultaneous quantification of geniposide and its active metabolite genipin in rat plasma and its application to a pharmacokinetic study

Genipin (GP), an active metabolite of geniposide (GE), exhibits more potent pharmacological effects than its parent compound. In this paper, a sensitive LC-MS/MS method was developed and fully validated for the simultaneous determination of GE and GP in rat plasma. We found that GP degraded rapidly in rat plasma at room temperature as a result of irreversible binding with the endogenous nucleophiles in plasma. GP was stable when the sample’s pH was ≤4.0. The degradation of GP in rat plasma was well prevented by immediate addition of 5% glacial acetic acid to the freshly collected plasma. The detection was performed on a tandem mass spectrometer coupled with electrospray ionization source in negative mode. Quantification was conducted by multiple reaction monitoring of the transitions [M + CH3COO]− m/z 447.3 225.3 for GE and [M − H]− m/z 225.2 123.1 for GP. The method exhibited high sensitivity (LLOQ 1 ng/mL for GE and 0.2 ng/mL for GP) by selecting the acetate adduct ions as the precursor ions for GE. The robust developed method was successfully applied to a pharmacokinetic study in rats after oral administration of GE.

Abstract

Genipin (GP), an active metabolite of geniposide (GE), exhibits more potent pharmacological effects than its parent compound. In this paper, a sensitive LC-MS/MS method was developed and fully validated for the simultaneous determination of GE and GP in rat plasma. We found that GP degraded rapidly in rat plasma at room temperature as a result of irreversible binding with the endogenous nucleophiles in plasma. GP was stable when the sample's pH was ≤4.0. The degradation of GP in rat plasma was well prevented by immediate addition of 5% glacial acetic acid to the freshly collected plasma. The detection was performed on a tandem mass spectrometer coupled with electrospray ionization source in negative mode. Quantification was conducted by multiple reaction monitoring of the transitions [M + CH3COO] m/z 447.3 [RIGHTWARDS ARROW] 225.3 for GE and [M − H] m/z 225.2 [RIGHTWARDS ARROW] 123.1 for GP. The method exhibited high sensitivity (LLOQ 1 ng/mL for GE and 0.2 ng/mL for GP) by selecting the acetate adduct ions as the precursor ions for GE. The robust developed method was successfully applied to a pharmacokinetic study in rats after oral administration of GE.

Throughput enhancement of parallel step emulsifier devices by shear-free and efficient nozzle clearance

Lab Chip, 2017, Accepted ManuscriptDOI: 10.1039/C7LC01037K, PaperElad Stolovicki, Roy Ziblat, David A. WeitzStep emulsification is an attractive method for production of monodisperse drops. Its main advantage is the ability to parallelize many step emu…

Lab Chip, 2017, Accepted Manuscript
DOI: 10.1039/C7LC01037K, Paper
Elad Stolovicki, Roy Ziblat, David A. Weitz
Step emulsification is an attractive method for production of monodisperse drops. Its main advantage is the ability to parallelize many step emulsifier nozzles to achieve high production rates. However, step...
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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.
This article is protected by copyright. All rights reserved

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.

This article is protected by copyright. All rights reserved

Effects of electrothermal vortices on insulator-based dielectrophoresis for circulating tumor cell separation

Insulator-based dielectrophoresis (iDEP) is a powerful technique for separation and manipulation of bioparticles. In recent years, iDEP designs using arrays of insulating posts have shown promising results toward reaching high-efficiency bioparticle manipulation. Joule heating (JH) and electrothermal (ET) flows have been observed in iDEP microdevices and significantly affecting their performances. In this research, we utilize mathematical modeling to study, iDEP technique and the effects of JH and ET flow on device performance and propose a separation scenario for selective trapping of circulating tumor cells (CTCs). A robust numerical model is developed to calculate the distribution of electric and fluid flow fields in the presence of JH and ET flow, and predict the cells’ trajectory inside the system. Our results indicate that JH not only induces temperature rise in the system, but also may alter the design iDEP separation scenario by inducing ET vortices that affect the cell’s trajectory. To investigate the impact of JH-induced ET flow characteristics and vortex generation on separation efficiency, we introduce a dimensionless force ratio encompassing the effects of electrical field, drag forces, JH, and ET flow. Interestingly, it was found that ET flows can be used to significantly enhance the separation efficiency, even in higher inlet flow rates. Lastly, the effect of post geometry has been discussed.

Abstract

Insulator-based dielectrophoresis (iDEP) is a powerful technique for separation and manipulation of bioparticles. In recent years, iDEP designs using arrays of insulating posts have shown promising results toward reaching high-efficiency bioparticle manipulation. Joule heating (JH) and electrothermal (ET) flows have been observed in iDEP microdevices and significantly affecting their performances. In this research, we utilize mathematical modeling to study, iDEP technique and the effects of JH and ET flow on device performance and propose a separation scenario for selective trapping of circulating tumor cells (CTCs). A robust numerical model is developed to calculate the distribution of electric and fluid flow fields in the presence of JH and ET flow, and predict the cells’ trajectory inside the system. Our results indicate that JH not only induces temperature rise in the system, but also may alter the design iDEP separation scenario by inducing ET vortices that affect the cell's trajectory. To investigate the impact of JH-induced ET flow characteristics and vortex generation on separation efficiency, we introduce a dimensionless force ratio encompassing the effects of electrical field, drag forces, JH, and ET flow. Interestingly, it was found that ET flows can be used to significantly enhance the separation efficiency, even in higher inlet flow rates. Lastly, the effect of post geometry has been discussed.

Addition of urea and thiourea to electrophoresis sample buffer improves efficiency of protein extraction from TCA/acetone-treated smooth muscle tissues for phos-tag SDS-PAGE

Phosphorylation analysis by using phos-tag technique has been reported to be suitable for highly sensitive quantification of smooth muscle myosin regulatory light chain (LC20) phosphorylation. However, there is another factor that will affect the sensitivity of phosphorylation analysis, that is, protein extraction. Here, we optimized the conditions for total protein extraction out of trichloroacetic acid (TCA)-fixed tissues. Standard SDS sample buffer extracted less LC20, actin and myosin phosphatase targeting subunit 1 (MYPT1) from TCA/acetone treated ciliary muscle strips. On the other hand, sample buffer containing urea and thiourea in addition to lithium dodecyl sulfate (LDS) or SDS extracted those proteins more efficiently, and thus increased the detection sensitivity up to 4–5 fold. Phos-tag SDS-PAGE separated dephosphorylated and phosphorylated LC20s extracted in LDS/urea/thiourea sample buffer to the same extent as those in standard SDS buffer. We have concluded that LDS (or SDS) /urea/thiourea sample buffer is suitable for highly sensitive phosphorylation analysis in smooth muscle, especially when it is treated with TCA/acetone.

Abstract

Phosphorylation analysis by using phos-tag technique has been reported to be suitable for highly sensitive quantification of smooth muscle myosin regulatory light chain (LC20) phosphorylation. However, there is another factor that will affect the sensitivity of phosphorylation analysis, that is, protein extraction. Here, we optimized the conditions for total protein extraction out of trichloroacetic acid (TCA)-fixed tissues. Standard SDS sample buffer extracted less LC20, actin and myosin phosphatase targeting subunit 1 (MYPT1) from TCA/acetone treated ciliary muscle strips. On the other hand, sample buffer containing urea and thiourea in addition to lithium dodecyl sulfate (LDS) or SDS extracted those proteins more efficiently, and thus increased the detection sensitivity up to 4–5 fold. Phos-tag SDS-PAGE separated dephosphorylated and phosphorylated LC20s extracted in LDS/urea/thiourea sample buffer to the same extent as those in standard SDS buffer. We have concluded that LDS (or SDS) /urea/thiourea sample buffer is suitable for highly sensitive phosphorylation analysis in smooth muscle, especially when it is treated with TCA/acetone.

An on-line coupling of nanofibrous extraction with column-switching high performance liquid chromatography – A case study on the determination of bisphenol A in environmental water samples

Publication date: 1 February 2018
Source:Talanta, Volume 178
Author(s): Martina Háková, Lucie Chocholoušová Havlíková, Jiří Chvojka, Petr Solich, Dalibor Šatínský
Polyamide 6 nanofiber polymers were used as modern sorbents for on-line solid phase extraction (SPE) coupled with liquid chromatography. The on-line SPE system was tested for the determination of bisphenol A in river water samples. Polyamide nanofibers were prepared using needleless electrospinning, inserted into a mini-column cartridge (5 × 4.6mm) and coupled with HPLC. The effect of column packing and the amount of polyamide 6 on extraction efficiency was tested and the packing process was optimized. The proposed method was performed using a 50-µL sample injection followed by an on-line nanofibrous extraction procedure. The influence of the washing mobile phase on the retention of bisphenol A during the extraction procedure was evaluated. Ascentis® Express C18 (10cm × 4.6mm) core-shell column was used as an analytical column. Fluorescence detection wavelengths (λex = 225nm and λem = 320nm) were used for identification and quantification of Bisphenol A in river waters. The linearity was tested in the range from 2 to 500µgL−1 (using nine calibration points). The limits of detection and quantification were 0.6 and 2µgL−1, respectively. The developed method was successfully used for the determination of bisphenol A in various samples of river waters in the Czech Republic (The Ohře, Labe, Nisa, Úpa, and Opava Rivers).

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Publication date: 1 February 2018
Source:Talanta, Volume 178

Author(s): Martina Háková, Lucie Chocholoušová Havlíková, Jiří Chvojka, Petr Solich, Dalibor Šatínský

Polyamide 6 nanofiber polymers were used as modern sorbents for on-line solid phase extraction (SPE) coupled with liquid chromatography. The on-line SPE system was tested for the determination of bisphenol A in river water samples. Polyamide nanofibers were prepared using needleless electrospinning, inserted into a mini-column cartridge (5 × 4.6mm) and coupled with HPLC. The effect of column packing and the amount of polyamide 6 on extraction efficiency was tested and the packing process was optimized. The proposed method was performed using a 50-µL sample injection followed by an on-line nanofibrous extraction procedure. The influence of the washing mobile phase on the retention of bisphenol A during the extraction procedure was evaluated. Ascentis® Express C18 (10cm × 4.6mm) core-shell column was used as an analytical column. Fluorescence detection wavelengths (λex = 225nm and λem = 320nm) were used for identification and quantification of Bisphenol A in river waters. The linearity was tested in the range from 2 to 500µgL−1 (using nine calibration points). The limits of detection and quantification were 0.6 and 2µgL−1, respectively. The developed method was successfully used for the determination of bisphenol A in various samples of river waters in the Czech Republic (The Ohře, Labe, Nisa, Úpa, and Opava Rivers).

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Carboxylated carbon nanospheres as solid-phase extraction adsorbents for the determination of perfluorinated compounds in water samples by liquid chromatography–tandem mass spectrometry

Publication date: 1 February 2018
Source:Talanta, Volume 178
Author(s): Xia Wang, Ying Zhang, Fu-Wei Li, Ru-Song Zhao
This work demonstrates the extraction potential of carboxylated carbon nanospheres (CNSs-COOH) for solid-phase extraction of perfluoroalkyl acids (PFAAs) for the first time. Six PFAAs, including perfluorohexanesulfonate (PFHxS), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorooctanoic sulfonic (PFOS), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA), were quantitatively adsorbed on a CNSs-COOH-packed cartridge; then, the PFAAs retained on the adsorbent were quantitatively eluted with an optimized volume of acetone (pH = 10). Finally, the desorbed PFAAs were determined by liquid chromatography–tandem mass spectrometry. Important relevant factors, such as the eluant and its volume, sample pH, amount of CNSs-COOH, sample flow rate and sample volume were optimized in detail. Under the optimized conditions, low limits of detection (0.01–1.2ngL−1), wide linear range (0.50–200ngL−1) and good repeatability (2.4–5.1%) and good reproducibility (3.7–8.8%) were obtained. The proposed method was applied to analyze the six PFAAs in real environmental water samples, and satisfactory results were achieved. All of these results showed that CNSs-COOH will be a good choice for the pre-concentration and analysis of target PFAAs at trace levels in environmental water samples in the future.

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Publication date: 1 February 2018
Source:Talanta, Volume 178

Author(s): Xia Wang, Ying Zhang, Fu-Wei Li, Ru-Song Zhao

This work demonstrates the extraction potential of carboxylated carbon nanospheres (CNSs-COOH) for solid-phase extraction of perfluoroalkyl acids (PFAAs) for the first time. Six PFAAs, including perfluorohexanesulfonate (PFHxS), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorooctanoic sulfonic (PFOS), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA), were quantitatively adsorbed on a CNSs-COOH-packed cartridge; then, the PFAAs retained on the adsorbent were quantitatively eluted with an optimized volume of acetone (pH = 10). Finally, the desorbed PFAAs were determined by liquid chromatography–tandem mass spectrometry. Important relevant factors, such as the eluant and its volume, sample pH, amount of CNSs-COOH, sample flow rate and sample volume were optimized in detail. Under the optimized conditions, low limits of detection (0.01–1.2ngL−1), wide linear range (0.50–200ngL−1) and good repeatability (2.4–5.1%) and good reproducibility (3.7–8.8%) were obtained. The proposed method was applied to analyze the six PFAAs in real environmental water samples, and satisfactory results were achieved. All of these results showed that CNSs-COOH will be a good choice for the pre-concentration and analysis of target PFAAs at trace levels in environmental water samples in the future.

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Quantitative analysis of drug distribution by ambient mass spectrometry imaging method with signal extinction normalization strategy and inkjet-printing technology

Publication date: 1 March 2018
Source:Talanta, Volume 179
Author(s): Zhigang Luo, Jingjing He, Jiuming He, Lan Huang, Xiaowei Song, Xin Li, Zeper Abliz
Quantitative mass spectrometry imaging (MSI) is a robust approach that provides both quantitative and spatial information for drug candidates’ research. However, because of complicated signal suppression and interference, acquiring accurate quantitative information from MSI data remains a challenge, especially for whole-body tissue sample. Ambient MSI techniques using spray-based ionization appear to be ideal for pharmaceutical quantitative MSI analysis. However, it is more challenging, as it involves almost no sample preparation and is more susceptible to ion suppression/enhancement. Herein, based on our developed air flow-assisted desorption electrospray ionization (AFADESI)-MSI technology, an ambient quantitative MSI method was introduced by integrating inkjet-printing technology with normalization of the signal extinction coefficient (SEC) using the target compound itself. The method utilized a single calibration curve to quantify multiple tissue types. Basic blue 7 and an antitumor drug candidate (S-(+)-deoxytylophorinidine, CAT) were chosen to initially validate the feasibility and reliability of the quantitative MSI method. Rat tissue sections (heart, kidney, and brain) administered with CAT was then analyzed. The quantitative MSI analysis results were cross-validated by LC-MS/MS analysis data of the same tissues. The consistency suggests that the approach is able to fast obtain the quantitative MSI data without introducing interference into the in-situ environment of the tissue sample, and is potential to provide a high-throughput, economical and reliable approach for drug discovery and development.

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Publication date: 1 March 2018
Source:Talanta, Volume 179

Author(s): Zhigang Luo, Jingjing He, Jiuming He, Lan Huang, Xiaowei Song, Xin Li, Zeper Abliz

Quantitative mass spectrometry imaging (MSI) is a robust approach that provides both quantitative and spatial information for drug candidates’ research. However, because of complicated signal suppression and interference, acquiring accurate quantitative information from MSI data remains a challenge, especially for whole-body tissue sample. Ambient MSI techniques using spray-based ionization appear to be ideal for pharmaceutical quantitative MSI analysis. However, it is more challenging, as it involves almost no sample preparation and is more susceptible to ion suppression/enhancement. Herein, based on our developed air flow-assisted desorption electrospray ionization (AFADESI)-MSI technology, an ambient quantitative MSI method was introduced by integrating inkjet-printing technology with normalization of the signal extinction coefficient (SEC) using the target compound itself. The method utilized a single calibration curve to quantify multiple tissue types. Basic blue 7 and an antitumor drug candidate (S-(+)-deoxytylophorinidine, CAT) were chosen to initially validate the feasibility and reliability of the quantitative MSI method. Rat tissue sections (heart, kidney, and brain) administered with CAT was then analyzed. The quantitative MSI analysis results were cross-validated by LC-MS/MS analysis data of the same tissues. The consistency suggests that the approach is able to fast obtain the quantitative MSI data without introducing interference into the in-situ environment of the tissue sample, and is potential to provide a high-throughput, economical and reliable approach for drug discovery and development.

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Application of ESI-HRMS for molybdenum speciation in natural waters: An investigation of molybdate-halide reactions

Publication date: 1 March 2018 Source:Talanta, Volume 179 Author(s): Duc Huy Dang, R. Douglas Evans High resolution electrospray ionization mass spectrometry (ESI-HRMS) was used to study the speciation of molybdate in interaction w…

Publication date: 1 March 2018
Source:Talanta, Volume 179

Author(s): Duc Huy Dang, R. Douglas Evans

High resolution electrospray ionization mass spectrometry (ESI-HRMS) was used to study the speciation of molybdate in interaction with halides (Cl, F, Br). Desolvation during electrospray ionization induced alteration of aqueous species but method optimization successfully suppressed artefact compounds. At low Mo concentrations, chloro(oxo)molybdate and fluoro(oxo)molybdate species were found and in natural samples, MoO3Cl was detected for the first time, to the best of our knowledge. Apparent equilibrium constants for Cl substitution on molybdate were calculated for a range of pH values from 4.5 to 8.5. A minor alteration in speciation during the gas phase (conversion of doubly charged MoO4 2- to HMoO4 -) did not allow investigation of the molybdate acid-base properties; however this could be determined by speciation modeling. This study provides further evidence that ESI-HRMS is a fast and suitable tool to Deceasedassess the speciation of inorganic compounds such as Mo.

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A novel electrochemiluminescence sensor coupled with capillary electrophoresis for simultaneous determination of quinapril hydrochloride and its metabolite quinaprilat hydrochloride in human plasma

Publication date: 1 March 2018
Source:Talanta, Volume 179
Author(s): Shuangjiao Sun, Yanfen Wei, Hao Wang, Yupin Cao, Biyang Deng
A novel electrochemiluminescence (ECL) sensor with composite consisted of silica-sol, Zinc oxide nanoparticles (ZnO NPs), polyvinylpyrrolidone (PVP) and tris(2, 2′-bipyridine) ruthenium (II) was constructed. A new method for simultaneous determination of quinapril hydrochloride (QHCl) and its metabolite quinaprilat hydrochloride (QTHCl) in human plasma was developed using the ECL sensor coupled with capillary electrophoresis (CE). ECL intensities of QHCl and QTHCl increased dramatically when the ECL sensor was used as working electrode. The running buffer contains 14mmol/L phosphate (pH 8.0) and 20% n-propyl alcohol. Under optimized experimental conditions, the linearity ranges of the method are 0.007–8.0μg/mL for QHCl and 0.009–8.3μg/mL for QTHCl. The detection limits of QHCl and QTHCl (S/N=3) are 3.6ng/mL and 3.9ng/mL, respectively. The method was applied for the simultaneous determination of QHCl and QTHCl in human plasma with satisfactory results.

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Publication date: 1 March 2018
Source:Talanta, Volume 179

Author(s): Shuangjiao Sun, Yanfen Wei, Hao Wang, Yupin Cao, Biyang Deng

A novel electrochemiluminescence (ECL) sensor with composite consisted of silica-sol, Zinc oxide nanoparticles (ZnO NPs), polyvinylpyrrolidone (PVP) and tris(2, 2′-bipyridine) ruthenium (II) was constructed. A new method for simultaneous determination of quinapril hydrochloride (QHCl) and its metabolite quinaprilat hydrochloride (QTHCl) in human plasma was developed using the ECL sensor coupled with capillary electrophoresis (CE). ECL intensities of QHCl and QTHCl increased dramatically when the ECL sensor was used as working electrode. The running buffer contains 14mmol/L phosphate (pH 8.0) and 20% n-propyl alcohol. Under optimized experimental conditions, the linearity ranges of the method are 0.007–8.0μg/mL for QHCl and 0.009–8.3μg/mL for QTHCl. The detection limits of QHCl and QTHCl (S/N=3) are 3.6ng/mL and 3.9ng/mL, respectively. The method was applied for the simultaneous determination of QHCl and QTHCl in human plasma with satisfactory results.

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