Validation of a liquid chromatography‐triple quadrupole mass spectrometric method for the determination of 5‐nitro‐5′‐hydroxy‐indirubin‐3′‐oxime (AGM‐130) in human plasma and its application to microdose clinical trial

A liquid chromatography–triple quadrupole mass spectrometric (LC‐MS/MS) method was developed and validated for the determination of 5‐nitro‐5′‐hydroxy‐indirubin‐3′‐oxime (AGM‐130) in human plasma to support a microdose clinical trial. The method consisted of a liquid–liquid extraction for sample preparation and LC‐MS/MS analysis in the positive ion mode using TurboIonSpray^TM for analysis. d₃‐AGM‐130 was used as the internal standard. A linear regression (weighted 1/concentration) was used to fit calibration curves over the concentration range of 10–2000 pg/mL for AGM‐130. There were no endogenous interference components in the blank human plasma tested. The accuracy at the lower limit of quantitation was 96.6% with a precision (coefficient of variation, CV) of 4.4%. For quality control samples at 30, 160 and 1600 pg/mL, the between run CV was ≤5.0 %. Between‐run accuracy ranged from 98.1 to 101.0%. AGM‐130 was stable in 50% acetonitrile for 168 h at 4°C and 6 h at room temperature. AGM‐130 was also stable in human plasma at room temperature for 6 h and through three freeze–thaw cycles. The variability of selected samples for the incurred sample reanalysis was ≤12.7% when compared with the original sample concentrations. This validated LC‐MS/MS method for determination of AGM‐130 was used to support a phase 0 microdose clinical trial. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitation of SAR97276 in mouse tissues by rapid resolution liquid chromatography‐mass spectrometry

1,12‐Bis[5‐(2‐hydroxyethyl)‐4‐methyl‐1,3‐thiazol‐3‐ium]dodecane dibromide (SAR97276, T3) is a new antimalarial drug, which is currently being evaluated in clinical trials for severe malaria. Drug accumulation inside the parasite and a dual mechanism of action are a major strength of this compound, as it could help delay the development of resistance. The purpose of this article was to develop a rapid resolution LC‐MS method for quantifying SAR97276 in mouse tissues. The LC system consisted of Zorbax Eclipse XDB C8 (1.8 μm, 50×4.6 mm, 60°C) column. Elution with a gradient mobile phase consisting of ACN–trimethylamine‐formate buffer (pH 3) at a flow rate of 1 mL/min yielded sharp, utmost‐resolved peaks within 2 min. Tissue samples were powdered under liquid nitrogen. After protein precipitation with citric acid, SPE using WCX cartridges was used for sample preparation. There was no influence of the matrix on the detection of either SAR97276 or the IS. Assay precision was <13% and accuracy was 90–107%. The lower LOQs were 3.3 μg/kg in brain and 33 μg/kg in liver and heart. This newly developed method was used to study the tissue distribution of SAR97276 in mouse as part of the ongoing development of SAR97276.     

A rapid MCM‐41 dispersive micro‐solid phase extraction coupled with LC/MS/MS for quantification of ketoconazole and voriconazole in biological fluids

A rapid dispersive micro‐solid phase extraction (D‐μ‐SPE) combined with LC/MS/MS method was developed and validated for the determination of ketoconazole and voriconazole in human urine and plasma samples. Synthesized mesoporous silica MCM‐41 was used as sorbent in d ‐μ‐SPE of the azole compounds from biological fluids. Important D‐μ‐SPE parameters, namely type desorption solvent, extraction time, sample pH, salt addition, desorption time, amount of sorbent and sample volume were optimized. Liquid chromatographic separations were carried out on a Zorbax SB‐C₁₈ column (2.1 × 100 mm, 3.5 μm), using a mobile phase of acetonitrile–0.05% formic acid in 5 mm ammonium acetate buffer (70:30, v /v). A triple quadrupole mass spectrometer with positive ionization mode was used for the determination of target analytes. Under the optimized conditions, the calibration curves showed good linearity in the range of 0.1–10,000 μg/L with satisfactory limit of detection (≤0.06 μg/L) and limit of quantitation (≤0.3 μg/L). The proposed method also showed acceptable intra‐ and inter‐day precisions for ketoconazole and voriconazole from urine and human plasma with RSD ≤16.5% and good relative recoveries in the range 84.3–114.8%. The MCM‐41‐D‐μ‐SPE method proved to be rapid and simple and requires a small volume of organic solvent (200 μL); thus it is advantageous for routine drug analysis.     

A rapid and sensitive LC–MS/MS method for quantification of quercetin‐3‐O‐β‐d‐glucopyranosyl‐7‐O‐β‐d‐gentiobioside in plasma and its application to a pharmacokinetic study

A rapid and sensitive LC–MS/MS method with good accuracy and precision was developed and validated for the pharmacokinetic study of quercetin‐3‐O‐β‐d ‐glucopyranosyl‐7‐O‐β‐d ‐gentiobioside (QGG) in Sprague–Dawley rats. Plasma samples were simply precipitated by methanol and then analyzed by LC–MS/MS. A Venusil® ASB C₁₈ column (2.1 × 50 mm, i.d. 5 μm) was used for separation, with methanol–water (50:50, v/v) as the mobile phase at a flow rate of 300 μL/min. The optimized mass transition ion‐pairs (m/z) for quantitation were 787.3/301.3 for QGG, and 725.3/293.3 for internal standard. The linear range was 7.32–1830 ng/mL with an average correlation coefficient of 0.9992, and the limit of quantification was 7.32 ng/mL. The intra‐ and inter‐day precision and accuracy were less than ±15%. At low, medium and high quality control concentrations, the recovery and matrix effect of the analyte and IS were in the range of 89.06–92.43 and 88.58–97.62%, respectively. The method was applied for the pharmacokinetic study of QGG in Sprague–Dawley rats. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of spiramycin and neospiramycin antibiotic residues in raw milk using LC/ESI‐MS/MS and solid‐phase extraction

A simple confirmatory method for the determination of spiramycin and its metabolite neospiramycin in raw milk using LC ESI MS/MS is presented. Macrolide residues in raw milk were extracted by ACN, and sample extracts were further cleaned up and concentrated using SPE cartridges. Both spiramycin and neospiramycin were protonated in electrospray positive ion mode to form singly and/or doubly charged pseudomolecular ions. Data acquisition was achieved using multiple reaction monitoring, i.e., two transitions, for quantification and confirmation. Matrix‐matched standard calibration curves were utilized to achieve the best accuracy for the method. The method performance was evaluated according to both a conventional validation procedure and a designed experimental result. The measurement uncertainty arising from accuracy and precision was estimated. The method accuracy, expressed as a percentage of an overall recovery, was from 82.1 to 108.8%, and its intermediate precision was less than 20%. LC/ESI‐MS/MS method LODs (S/N ? 3:1) of spiramycin and neospiramycin were less than 1.0 μg/kg.     

UPLC‐MS/MS assay for the simultaneous quantification of carvedilol and its active metabolite 4′‐hydroxyphenyl carvedilol in human plasma to support a bioequivalence study in healthy volunteers

An ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method has been developed for the simultaneous determination of carvedilol and its pharmacologically active metabolite 4′‐hydroxyphenyl carvedilol in human plasma using their deuterated internal standards (IS). Samples were prepared by solid‐phase extraction using 100 μL human plasma. Chromatographic separation of analytes was achieved on UPLC C18 (50 × 2.1 mm, 1.7 µm) column using acetonitrile‐4.0 mm ammonium formate, pH 3.0 adjusted with 0.1% formic acid (78:22, v/v) as the mobile phase. The multiple reaction monitoring transitions for both the analytes and IS were monitored in the positive electrospray ionization mode. The method was validated over a concentration range of 0.05–50 ng/mL for carvedilol and 0.01‐10 ng/mL for 4′‐hydroxyphenyl carvedilol. Intra‐ and inter‐batch precision (% CV) and accuracy for the analytes varied from 0.74 to 3.88 and 96.4 to 103.3% respectively. Matrix effect was assessed by post‐column analyte infusion and by calculation of precision values (coefficient of variation) in the measurement of the slope of calibration curves from eight plasma batches. The assay recovery was within 94–99% for both the analytes and IS. The method was successfully applied to support a bioequivalence study of 12.5 mg carvedilol tablets in 34 healthy subjects. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of a hydrophilic paclitaxel derivative, 7‐xylosyl‐10‐deacetylpaclitaxel in rat plasma by LC–MS/MS

A LC‐MS/MS method for the determination of a hydrophilic paclitaxel derivative 7‐xylosyl‐10‐deacetylpaclitaxel in rat plasma was developed to evaluate the pharmacokinetics of 7‐xylosyl‐10‐deacetylpaclitaxel in the rats. 7‐Xylosyl‐10‐deacetylpaclitaxel and docetaxel (IS for 7‐xylosyl‐10‐deacetylpaclitaxel) were extracted from rat plasma with acetic ether and analyzed on a Hypersil C₁₈ column (4.6 × 150 mm i.d., particle size 5 µm) with the mobile phase of ACN/0.05% formic acid (50:50, v/v). The analytes were detected using an ESI MS/MS in the multiple reaction monitoring mode. The standard curves for 7‐xylosyl‐10‐deacetylpaclitaxel in plasma were linear (r >0.999) over the concentration range of 2.0–1000 ng/mL with a weighting of 1/concentration². The method showed a satisfactory sensitivity (2.0 ng/mL using 50 µL plasma), precision (CV ≤ 10.1%), accuracy (relative error ?12.4 to 12.0%), and selectivity. This method was successfully applied to the pharmacokinetic study of 7‐xylosyl‐10‐deacetylpaclitaxel in rat plasma after intravenous administration of 7‐xylosyl‐10‐deacetylpaclitaxel to female Wistar rats. Copyright © 2008 John Wiley & Sons, Ltd.     

Lithium adduct as precursor ion for sensitive and rapid quantification of 20 (S)‐protopanaxadiol in rat plasma by liquid chromatography/quadrupole linear ion trap mass spectrometry and application to rat pharmacokinetic study

A novel, rapid and sensitive liquid chromatography/quadrupole linear ion trap mass spectrometry [LC‐ESI‐(QqLIT)MS/MS] method was developed and validated for the quantification of protopanaxadiol (PPD) in rat plasma. Oleanolic acid (OA) was used as internal standard (IS). A simple protein precipitation based on acetonitrile (ACN) was employed. Chromatographic separation was performed on a Sepax GP‐C₁₈ column (50 × 2.1 mm, 5 μM) with a mobile phase consisting of ACN–water and 1.5 μM formic acid and 25 mM lithium acetate (90 : 10, v/v) at a flow rate of 0.4 ml/min for 3.0 min. Multiple‐reaction‐monitoring mode was performed using lithium adduct ion as precursor ion of m/z 467.5/449.4 and 455.6/407.4 for the drug and IS, respectively. Calibration curve was recovered over a concentration range of 0.5–100 ng/ml with a correlation coefficient >0.99. The limit of detection was 0.2 ng/ml in rat plasma for PPD. The results of the intraday and interday precision and accuracy studies were well within the acceptable limits. The validated method was successfully applied to investigate the pharmacokinetic study of PPD after intravenous and gavage administration to rat. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantitation and pharmacokinetics of 1,4‐diamino‐2,3‐dicyano‐1,4‐bis (2‐aminophenylthio) butadiene (U0126) in rat plasma by liquid chromatography‐tandem mass spectrometry

A simple, robust, and rapid LC‐MS/MS method was developed for the quantitation of U0126 and validated in rat plasma. Plasma samples (20 μL) were deproteinized using 200 μL ACN containing 30 ng/mL of chlorpropamide, internal standard. Chromatographic separation performed on an Agilent Poroshell 120 EC‐C₁₈ column (4.6 × 50 mm, 2.7 μm particle size) with an isocratic mobile phase consisting of a 70:30 v/v mixture of ACN and 0.1% aqueous formic acid. Each sample was run at 0.6 mL/min for a total run time of 2 min per sample. Detection and quantification were performed using a mass spectrometer in selected reaction‐monitoring mode with positive ESI at m/z 381 → 123.9 for U0126 and m/z 277 → 175 for the internal standard. The standard curve was linear over a concentration range of 20–5000 ng/mL with correlation coefficients greater than 0.9965. Precision, both intra‐ and interday, was less than 10.1% with an accuracy of 90.7–99.4%. No matrix effects were observed. U0126 in rat plasma degraded approximately 41.3% after 3‐h storage at room temperature. To prevent degradation, sample handling should be on an ice bath and all solutions kept at 4°C. This method was successfully applied to a pharmacokinetic study of U0126 at various doses in rats.     

Simultaneous determination of multiveterinary drug residues in pork meat by liquid chromatography‐tandem mass spectrometry combined with solid phase extraction

An LC‐MS/MS method developed for simultaneous analysis of 54 veterinary drug residues of six families in pork meat samples, including sulfanilamide, nitroimidazoles, quinolones, macrolide antibiotics, lincosamides, and praziquantel. The pork meat sample was prepared by extraction with ACN, and clean‐up on a C₁₈ SPE cartridge. The sample was separated on a C₈ column and eluted with ACN, methanol, and formic acid. The MS/MS detector is operated in the multiple reaction monitoring mode, acquiring two specific precursor‐product ion transitions per target compound. The method showed excellent linearity (R² ≥ 0.99) and high precision (relative SD, RSD ≤ 19.8%) for all compounds. The method quantification limits of 54 veterinary drug residues were in the range of 0.3–3.0 μg/kg. Recoveries for most analytes based on matrix‐matched calibration in matrices were 20.9–121.0%. This method has been successfully applied for analysis of more than 100 pork meat samples from the local market; five of the 54 drugs were detected.     

The development and validation of a high‐throughput LC–MS/MS method for the analysis of endogenous β‐hydroxy‐β‐methylbutyrate in human plasma

A high‐throughput, sensitive, and rugged liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the rapid quantitation of β ‐hydroxy‐β ‐methylbutyrate (HMB) in human plasma has been developed and validated for routine use. The method uses 100 μL of plasma sample and employs protein precipitation with 0.1% formic acid in methanol for the extraction of HMB from plasma. Sample extracts were analyzed using LC–MS/MS technique under negative mode electrospray ionization conditions. A ¹³C–labeled stable isotope internal standard was used to achieve accurate quantitation. Multiday validation was conducted for precision, accuracy, linearity, selectivity, matrix effect, dilution integrity (2×), extraction recovery, freeze–thaw sample stability (three cycles), benchtop sample stability (6 h and 50 min), autosampler stability (27 h) and frozen storage sample stability (146 days). Linearity was demonstrated between 10 and 500 ng/mL. Inter‐day accuracies and coefficients of variation (CV) were 91.2–98.1 and 3.7–7.8%, respectively. The validated method was proven to be rugged for routine use to quantify endogenous levels of HMB in human plasma obtained from healthy volunteers.     

Highly sensitive determination of Schisandrin and Schisandrin B in plasma of rats after administration of Wurenchun (Fructus Schisandrae Chinensis Extracts) preparations by LC‐ESI‐MS/MS

A sensitive and specific method based on liquid chromatography‐tandem mass spectrometry using electrospray ionization (LC‐ESI‐MS/MS) has been developed for the determination of Schisandrin and Schisandrin B in rat plasma. A 100 μL plasma sample was extracted by methyl tert‐butyl ether after spiking the samples with nimodipine (internal standard) and performed on an XTerra®MS‐C₁₈ column (150 mm × 2.1 mm, 3.5 μm) with the mobile phase of acetonitrile–water–formic acid (80:20:0.2, v/v) at a flow rate of 0.2 mL/min in a run time of 8.5 min. The lower limit of quantification of the method was 40 ng/mL for Schisandrin and 20 ng/mL for Schisandrin B. The method showed reproducibility with intra‐day and inter‐day precision of less than 13.8% RSD, as well as accuracy, with inter‐ and intra‐assay accuracies between 93.5 and 107.2%. Finally, the LC‐ESI‐MS/MS method was successfully applied to study the pharmacokinetics of Schisandrin and Schisandrin B in rats after administration of Wurenchun commercial formulations to rats. Copyright © 2009 John Wiley & Sons, Ltd.     

Simultaneous LC‐MS/MS bioanalysis of etoposide and paclitaxel in mouse tissues and plasma after oral administration of self‐microemulsifying drug‐delivery systems

In this study, a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and validated to simultaneously determine the anticancer drugs etoposide and paclitaxel in mouse plasma and tissues including liver, kidney, lung, heart, spleen and brain. The analytes were extracted from the matrices of interest by liquid–liquid extraction using methyl tert‐butyl ether–dichloromethane (1:1, v/v). Chromatographic separation was achieved on an Ultimate XB‐C₁₈ column (100 × 2.1 mm, 3 μm) at 40°C and the total run time was 4 min under a gradient elution. Ionization was conducted using electrospray ionization in the positive mode. Stable isotope etoposide‐d3 and docetaxel were used as the internal standards. The lower limit of quantitation (LLOQ) of etoposide was 1 ng/g tissue for all tissues and 0.5 ng/mL for plasma. The LLOQ of paclitaxel was 0.4 ng/g tissue and 0.2 ng/mL for all tissues and plasma, respectively. The coefficients of correlation for all of the analytes in the tissues and plasma were >0.99. Both intra‐ and inter‐day accuracy and precision were satisfactory. This method was successfully applied to measure plasma and tissue drug concentrations in mice treated with etoposide and paclitaxel‐loaded self‐microemulsifying drug‐delivery systems.     

Quantification and application of a liquid chromatography–tandem mass spectrometric method for the determination of WKYMVm peptide in rat using solid‐phase extraction

A liquid chromatographic–electrospray ionization–time‐of‐flight/mass spectrometric (LC‐ESI‐TOF/MS) method was developed and applied for the determination of WKYMVm peptide in rat plasma to support preclinical pharmacokinetics studies. The method consisted of micro‐elution solid‐phase extraction (SPE) for sample preparation and LC‐ESI‐TOF/MS in the positive ion mode for analysis. Phenanthroline (10 mg/mL) was added to rat blood immediately for plasma preparation followed by addition of trace amount of 2 m hydrogen chloride to plasma before SPE for stability of WKYMVm peptide. Then sample preparation using micro‐elution SPE was performed with verapamil as an internal standard. A quadratic regression (weighted 1/concentration²), with the equation y = ax² + bx + c was used to fit calibration curves over the concentration range of 3.02–2200 ng/mL for WKYMVm peptide. The quantification run met the acceptance criteria of ±25% accuracy and precision values. For quality control samples at 15, 165 and 1820 ng/mL from the quantification experiment, the within‐run and the between‐run accuracy ranged from 92.5 to 123.4% with precision values ≤15.1% for WKYMVm peptide from the nominal values. This novel LC‐ESI‐TOF/MS method was successfully applied to evaluate the pharmacokinetics of WKYMVm peptide in rat plasma.     

A new,validated HPLC‐MS/MS method for the simultaneous determination of the anti‐cancer agent capecitabine and its metabolites: 5′‐deoxy‐5‐fluorocytidine, 5′‐deoxy‐5‐fluorouridine, 5‐fluorouracil and 5‐fluorodihydrouracil,in human plasma

A rapid and selective liquid chromatography/tandem mass spectrometric method was developed for the simultaneous determination of capecitabine and its metabolites 5′‐deoxy‐5‐fluorocytidine (5′‐DFCR), 5′‐deoxy‐5‐fluorouracil (5′‐DFUR), 5‐fluorouracil (5‐FU) and dihydro‐5‐fluorouracil (FUH₂) in human plasma. A 200 μL human plasma aliquot was spiked with a mixture of internal standards fludarabine and 5‐chlorouracil. A single‐step protein precipitation method was employed using 10% (v/v) trichloroacetic acid in water to separate analytes from bio‐matrices. Volumes of 20 μL of the supernatant were directly injected onto the HPLC system. Separation was achieved on a 30 × 2.1 mm Hypercarb (porous graphitic carbon) column using a gradient by mixing 10 mm ammonium acetate and acetonitrile–2‐propanol–tetrahydrofuran (1 : 3 : 2.25, v/v/v). The detection was performed using a Finnigan TSQ Quantum Ultra equipped with the electrospray ion source operated in positive and negative mode. The assay quantifies a range from 10 to 1000 ng/mL for capecitabine, from 10 to 5000 ng/mL for 5′‐DFCR and 5′‐DFUR, and from 50 to 5000 ng/mL for 5‐FU and FUH₂ using a plasma sample of 200 μL. Correlation coefficients (r²) of the calibration curves in human plasma were better than 0.99 for all compounds. At all concentration levels, deviations of measured concentrations from nominal concentration were between ?4.41 and 3.65% with CV values less than 12.0% for capecitabine, between ?7.00 and 6.59% with CV values less than 13.0 for 5′‐DFUR, between ?3.25 and 4.11% with CV values less than 9.34% for 5′‐DFCR, between ?5.54 and 5.91% with CV values less than 9.69% for 5‐FU and between ?4.26 and 6.86% with CV values less than 14.9% for FUH₂. The described method was successfully applied for the evaluation of the pharmacokinetic profile of capecitabine and its metabolites in plasma of treated cancer patients. Copyright © 2009 John Wiley & Sons, Ltd.     

Fast liquid chromatography separation and multiple‐reaction monitoring mass spectrometric detection of neurotransmitters

We describe here the fast LC‐MS/MS separation of a mixture of neurotransmitters consisting of dopamine, epinephrine, norepinephrine, 3,4‐dihydroxybenzylamine (DHBA), salsolinol, serotonin, and γ‐aminobutyric acid (GABA). The new UltiMate® 3000 Rapid Separation system (RSLC) was successfully coupled to the 4000 QTRAP mass spectrometer operating in multiple‐reaction monitoring (MRM) mode. The separation was attained using a 100 mm length, 2.2 μm particle size Acclaim column at a flow rate of 0.5 mL/min. The column back pressure was 350 bar, while the total run time including column re‐equilibration was 5.2 min. The peak resolution was minimally affected by the fast separation. The RSLC‐MRM separation was found to have a precision range based on peak area for 50 replicate runs of 2–5% CV for all analytes, and the reproducibility of the retention time for all analytes was found to range from 0–2% CV. The described method represents an almost seven times shorter analysis time of neurotransmitters using LC/MRM which is very useful in screening large quantities of biological samples for various neurotransmitters.     

Multi‐mycotoxin analysis in complex biological matrices using LC‐ESI/MS: Experimental study using triple stage quadrupole and LTQ‐Orbitrap

In the present study, we report the application of LC‐MS based on two different LC‐MS systems to mycotoxin analysis. The mycotoxins were extracted with an ACN/water/acetic acid mixture and directly injected into a LC‐MS/MS system without any dilution procedure. First, a sensitive and reliable HPLC‐ESI‐MS/MS method using selected reaction monitoring on a triple quadrupole mass spectrometer (TSQ Quantum Ultra AM) has been developed for determining 32 mycotoxins in crude extracts of wheat and maize. This method was operated both in positive and in negative ionization modes in two separate chromatographic runs. The method was validated by studies of spiked recoveries, linearity, matrix effect, intra‐assay precision and sensitivity. Further, we have developed and evaluated a method based on accurate mass measurements of extracted target ions in full scan mode using micro‐LC‐LTQ‐Orbitrap as a tool for fast quantitative analysis. Both instruments exhibited very high sensitivity and repeatability in positive ionization mode. Coupling of micro‐LC to Orbitrap technology was not applicable to the negatively ionizable compounds. The LC triple quadrupole MS method has proved to be stable in quantitation, as it is with respect to the matrix effects of grain samples.     

Performance of zwitterionic hydrophilic interaction LC for the determination of iodinated X‐ray contrast agents

This study compares the separation performance of a group of iodinated X‐ray contrast media on four different columns. The first three were two stationary phases (SPs) modified with C₁₈ and a polar‐embedded SP (polar amide group bonded to an alkyl chain), all of which worked under RP‐LC mode. The fourth was a zwitterionic sulphoalkylbetaine SP, working under the hydrophilic interaction LC (HILIC) mode. After the optimisation of the different parameters, the zwitterionic column displayed the best separation, which also overcomes the problems encountered when these analytes were separated under RP‐LC. Moreover, when HILIC is coupled to MS/MS, sensitivity is enhanced. However, when sewage samples were analysed by SPE followed by the optimal HILIC–MS/MS, the sensitivity of the method was affected due to the high matrix effect, which had to be solved by dilution of the extract. Finally, the method was preliminarily validated with sewage and the figures of merit were comparable to those of the SPE–RP‐LC–MS/MS.     

A simple LC–MS/MS method facilitated by salting‐out assisted liquid–liquid extraction to simultaneously determine trans‐resveratrol and its glucuronide and sulfate conjugates in rat plasma and its application to pharmacokinetic assay

A simple LC–MS/MS method facilitated by salting‐out assisted liquid–liquid extraction (SALLE) was applied to simultaneously investigate the pharmacokinetics of trans‐ resveratrol (Res) and its major glucuronide and sulfate conjugates in rat plasma. Acetonitrile–methanol (80:20, v /v) and ammonium acetate (10 mol L⁻¹) were used as extractant and salting‐out reagent to locate the target analytes in the supernatant after the aqueous and organic phase stratification, then the analytes were determined via gradient elution by LC–MS/MS in negative mode in a single run. The analytical method was validated with good selectivity, acceptable accuracy (>85%) and low variation of precision (<15%). SALLE showed better extraction efficiency of target glucuronide and sulfate conjugates (>80%). The method was successfully applied to determine Res and its four conjugated metabolites in rat after Res administration (intragastric, 50 mg kg⁻¹; intravenous, 10 mg kg⁻¹). The systemic exposures to Res conjugates were much higher than those to Res (AUC_0–t , i.v., 7.43 μm h; p.o., 8.31 μm h); Res‐3‐O‐β ‐d ‐glucuronide was the major metabolite (AUC_0–t , i.v., 66.1 μm h; p.o., 333.4 μm h). The bioavailability of Res was estimated to be ~22.4%. The reproducible SALLE method simplified the sample preparation, drastically improved the accuracy of the concomitant assay and gave full consideration of extraction recovery to each target analyte in bio‐samples.     

Simultaneous determination of 103 pesticide residues in tea samples by LC‐MS/MS

A simple and sensitive method was developed and validated for the simultaneous determination of 103 pesticide residues in tea by LC‐MS/MS. For the analysis of the pesticide with polarity, thermal lability or low volatility, this LC‐MS/MS method has an advantage over GC. In this work, residual pesticides were extracted from the tea sample with ACN and then purified using Carb‐NH₂ SPE cartridges. Using the multiple reaction monitoring mode, the pesticides were quantified and identified by the most abundant and characteristic fragment ions. The recoveries obtained for each pesticide ranged between 65 and 114% at three spiked concentration levels. The intra‐day precisions were lower than 19.6%. Good linear relationships were observed with the correlation coefficients r² >0.996 for all analytes. The established method was successfully applied to the determination of pesticide residues in real tea samples.