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A sensitive, selective, and reliable LC-MS/MS method was developed and validated for simultaneous quantification of venlafaxine (VEN) and its 5 metabolites (ODV, NDV, NNDDV, OHV and NODDV) in rat plasma. The calibration ranges are 15.0 to 6000 ng/mL for VEN, 1.00 to 400 ng/mL for ODV, 5.00 to 2000 ng/mL for NDV, 1.00 to 400 ng/mL for NNDDV, 10.0 to 4000 ng/mL for OHV, and 0.200 to 20.0 ng/mL for NODDV. Briefly, 50 μL of rat plasma was extracted using liquid-liquid extraction (LLE) with methyl tert -butyl ether (MTBE). The analytes were separated on an Agilent SB-Phenyl (50 mm × 4.6 mm, 3.5 μm) column using a binary gradient of 0.1% formic acid in water versus 0.1% formic acid in acetonitrile at a flow rate of 0.8 mL/min. The method was validated following FDA guidance for bioanalytical method validation. Validated method was successfully applied to a pharmacokinetic study of VEN orally administered to rats. [ABSTRACT FROM AUTHOR]

A high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) method was developed and fully validated for simultaneous determination of puerarin, 3′-hydroxy puerarin, 6″- O -xylosyl puerarin, 3′-methoxy puerarin, mirificin, puerarin-7- O -glucoside, daidzin, daidzein, daidzein-7- O -glucoside, ginsenoside-Rd, notoginsenoside-R1, ginsenoside-Re, ginsenoside-Rg1, ginsenoside-Rb1 in rat plasma after intravenous injection of 5 mL/kg Gegen-Sanqi compatibility solution (containing Pueraria flavonid 10.8 mg/mL and Panax notoginsenosidum 5.4 mg/mL). After addition of internal standard (IS) baicalin, the analytes and IS were recovered from rat plasma by protein precipitation using acetonitrile containing 0.1% formic acid. Chromatographic separation was performed on a Capcell pak MG C18 column (3.0 mm × 75 mm, 3.0 μm) at 35 °C with a flow rate of 0.75 mL/min. Mass spectrometry was conducted using multiple reaction monitoring in positive mode. The method was linear for all of the analytes over 1000 times concentration range with correlation coefficients greater than 0.99. The precision and accuracy of the LC–MS/MS assay based on the three analytical quality control (QC) levels were well within the acceptance criteria from FDA guidance for bioanalytical method validation. Method recoveries were higher than 75% and the matrix effects were minimal. All analytes were stable under tested conditions. It was the first time to study the pharmacokinetics of daidzein-7- O -glucoside in rat plasma. To the best of our knowledge, this is the first study for simultaneous determination of so many analytes in rat plasma after intravenous injection of Gegen-Sanqi compatibility solution. It was expected that the present work would provide some helpful references for the apprehension of the mechanism of action and further clinical efficacy studies of Gegen-Sanqi herb-pair. [ABSTRACT FROM AUTHOR]

Deoxyglycychloxazol (TY501) is a glycyrrhetinic acid derivative which exhibits high anti-inflammatory activity and reduced pseudoaldosteronism compared to glycyrrhetinic acid. In this study, a sensitive and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was established for the quantitation of TY501 in rat plasma. Plasma samples were treated by precipitating protein with methanol and supernatants were separated by a Symmetry C 8 column with the mobile phase consisting of methanol and 10 mM ammonium formate (containing 0.1% of formic acid) (90:10, v/v). The selected reaction monitoring (SRM) transitions were performed at m/z 647.4→191.2 for TY501 and m/z 473.3→143.3 for astragaloside aglycone (IS) in the positive ion mode with atmospheric pressure chemical ionization (APCI) source. Calibration curve was linear over the concentration range of 5–5000 ng/mL. The lower limit of quantification was 5 ng/mL. The mean recovery was over 88%. The intra- and inter-day precisions were lower than 6.0% and 12.8%, respectively, and the accuracy was within ±1.3%. TY501 was stable under usual storage conditions and handling procedure. The validated method has been successfully applied to a pharmacokinetic study after oral administration of TY501 to rats at a dosage of 10 mg/kg. [ABSTRACT FROM AUTHOR]

A sensitive, simple and rapid analytical method based on a liquid chromatography–tandem mass spetrometry (LC–MS/MS) has been established and validated for the determination of stachyose in rat plasma. Plasma samples were prepared by protein precipitation with acetonitrile. Separation of stachyose and nystose (internal standard, IS) was achieved using acetonitrile-water (55:45, v/v) as the mobile phase at a flow rate of 1 ml/min for 6 min on an Asahipak NH 2 P-50 4E column with an Asahipak NH2P-50G 4A guard column. Detection and quantification were conducted by LC–MS/MS method in the negative ion mode using multiple reaction monitoring (MRM) transitions at m / z [M–H] − 665.4 → 383.1 for stachyose and 665.5 → 485.0 for IS, respectively. The method was linear over the concentration ranges of 100–30000 ng/ml with a lower limit of quantification (LLOQ) of 100 ng/ml. The intra- and inter- day precision were all within 8.7% and the accuracy ranged from 97.2–108.4% and 98.3–102.4%, respectively. Stability studies indicated that stachyose was stable under short-term, long-term and three freeze-thaw storage conditions. The method was successfully applied to a pharmacokinetic study involving pulmonary administration of micronized Rehmannia glutinosa oligosaccharides (RGOS) to rats. [ABSTRACT FROM AUTHOR]

( E )-Methyl-4-aryl-4-oxabut-2-enoate (YH-8) is a novel PKnB protein kinase inhibitor with good anti-tuberculosis activity. To evaluate its pharmacokinetics in rats, a sensitive and selective high performance liquid chromatography–tandem mass spectrometric (LC--MS/MS) method has been developed and validated for the quantification of YH-8 in rat plasma for the first time. Samples were pre-treated using a liquid--liquid extraction with ethyl acetate and the chromatographic separation was performed on a C18 column by gradient elution with methanol--water as the mobile phase. YH-8 was detected using a tandem mass spectrometer in positive selected reaction monitoring (SRM) mode. Method validation revealed good linearity over the range of 1–500 ng/mL for YH-8 with a lower limit of quantification (LLOQ) of 1 ng/mL. Intra- and inter-day precision of YH-8 assay in rat plasma samples were 2.0%–6.8%, with accuracy of the method being 100.69%–106.18%. Stability test showed that when spiked into rat plasma, YH-8 was stable for 12 h at room temperature, for up to 15 days at −70 °C, and after three freeze-thaw cycles. Extracted samples were found to be stable over 12 h in an auto-sampler. The method was successfully applied to the pharmacokinetic study of YH-8 in rats after oral administration at 100 mg/kg and 200 mg/kg. [ABSTRACT FROM AUTHOR]

A simple and selective specific high-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for determination of isobavachalcone (IBC) in rat plasma was developed. Neobavaisoflavone was used as an internal standard (IS). After protein precipitation with acetonitrile (2:1, v/v), the analyte and IS were separated on a 2.6 μm Kinetex C 18 column (100 mm × 2.1 mm i.d., Phenomenex) by isocratic elution with acetonitrile:water (60:40, v/v) as the mobile phase at a flow rate of 0.2 mL/min. An electrospray ionization (ESI) source was applied and operated in the negative ion mode; multiple reactions monitoring (MRM) mode was used for quantification, and the target fragment ions m / z 323.0 → 118.9 for IBC and m / z 321.1 → 265.0 for the IS were chosen. Good linearity was observed in the concentration range of 3.79–484.5 ng/mL for IBC in rat plasma. The recovery of IBC in plasma was in the range of 81.2–89.8%. Intra-day and inter-day precision were both lower than 10%. This method was suitable for pharmacokinetic studies after oral administration of 80 mg/kg IBC in rats. We also obtained pharmacokinetic parameters and concentration–time profiles for IBC after oral administration of IBC in rats. [ABSTRACT FROM AUTHOR]

CAT ((+)-(13aS)-deoxytylophorinine) is a novel anticancer drug belonging to phenanthroindolizidine alkaloids. A sensitive and reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for simultaneous quantification of CAT and its pharmacologically active 3-O-desmethyl metabolite (S-4) was developed and validated in rat plasma using rotundine as the internal standard (IS). CAT, S-4 and IS were extracted by acetonitrile protein precipitation and separated on an Eclipse XDB-C18 column (1.8 μm, 4.6 mm × 50 mm) with acetonitrile–water (27:73, v/v) mobile phase containing 0.1% formic acid at a 0.4 mL/min flow rate. Positive ion electrospray ionization in multiple reaction monitoring mode was employed to measure CAT, S-4 and IS by monitoring the transitions m/z 364.2 → 70.1 for CAT, 350.1 → 70.1 for S-4 and 356.2 → 192.2 for IS. Good linear correlation ( r 2 > 0.991) was achieved for CAT and S-4 over the range of 0.214–128.16 and 0.044–11.00 ng/mL, respectively. The lower limit of quantification was 0.214 ng/mL for CAT and 0.044 ng/mL for S-4, using 50 μL rat plasma samples. The intra- and inter-day precisions were not exceed 15% and the accuracy ranged between 94.80% and 108.22%. The average extraction recoveries of both analytes were greater than 94.62%. The method was successfully applied to the pharmacokinetic study of CAT and S-4 in rats after oral administration. [ABSTRACT FROM AUTHOR]

A simple, rapid and sensitive high-performance liquid chromatography tandem mass-spectrometric method (LC-MS/MS) for the novel multiple tyrosine kinase inhibitor (TKI) cabozantinib was developed and validated using erlotinib as internal standard (IS). Plasma samples were pre-treated by liquid–liquid extraction with ethyl acetate. Separation was achieved on a reversed phase C18 column (50 × 2 mm, 5 μm) at ambient temperature using isocratic elution with acetonitrile-water (45:55, v/v) containing 5 mM ammonium formate buffer (finally adjusted to apparent pH* = 5.0 with formic acid) at a flow rate of 0.4 mL/min. The analytes were monitored by a triple quadrupole tandem mass spectrometer with electrospray ionization source in the positive ion mode. Calibration curve was linear ( r > 0.99) in a concentration range of 0.5–1000 ng/mL with the lower limit of quantification (LLOQ) of 0.5 ng/mL. Intra- and inter-day accuracy and precision were validated by relative error values (RE) and relative standard deviation values (RSD), respectively, which were both lower than the limit of 15%. This method was successfully applied to a pharmacokinetic study of cabozantinib in rats. [ABSTRACT FROM AUTHOR]

Nigella glandulifera Freyn et Sit is a folk medicinal plant, whose seeds show significant anticancer activities attributed to triterpene saponins and volatile oil. In this study, an in vitro cytotoxicity assay demonstrated that Nigella A, the major component of triterpene saponins extracted from N. glandulifera , exhibited growth inhibition in the human lung carcinoma A-549 cell line. Due to this potential activity, a reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method to quantify Nigella A in rat plasma for a pharmacokinetic study was developed. Nigella A and pravastatin, as internal standard (IS), were extracted from rat plasma using acetonitrile to precipitate protein. Separation was performed on an Agilent Zorbax SB-Aq (3.0 × 150 mm, 3.5 μm) column using a gradient elution method with acetonitrile–0.1% formic acid in water at a flow rate of 0.35 mL/min. Detection was performed using an electrospray ionization in a negative ion multiple reaction monitoring mode. The deprotonated precursor to product ion transitions monitored for Nigella A and IS was at m / z 1352.7→882.6 and m / z 423.1→321.0, respectively. The linear range was 0.240–120 μg/mL with a square regression coefficient ( r = 0.9996). The intra-day and inter-day precision was less than 6.93%. The simple extraction procedure provided recovery ranged from 92.32 to 95.44% for both analyte and IS. The method was proved to be reliable, precise, and accurate, and was successfully applied to a pharmacokinetic study of Nigella A in rats after i.v. administration via the tail vein at doses of 10, 20, and 30 mg/kg. [ABSTRACT FROM AUTHOR]

A rapid and sensitive LC-MS/MS method was developed for the quantification of vilazodone in rat plasma using escitalopram as internal standard. After extracted with organic solvent, post-treatment samples were chromatographed on an Agela C18 column. An isocratic mobile phase of acetonitrile: 5 mM ammonium acetate: formic acid (35:65:0.1, v/v/v) was applied at a flow rate of 0.25 mL/min. Detection was performed using multiple reaction-monitoring (MRM) modes at m/z 442.4 → 155.3 for vilazodone and m/z 325.1 → 109.0 for escitalopram. The method was linear in the concentration range of 1.0 - 100 ng/mL with a correlation coefficient ≥0.993. The intra- and inter-assay precision (%RSD) values were within 13.4%, and intra- and inter-day accuracy (%RE) ranged from -9.8 to 6.9%. The total analysis time was 2.2 min. The LC-MS/MS method was fully validated for its sensitivity, selectivity, stability, matrix effect and recovery. The data indicated that the developed method was rapid, specific and sensitive. This method was further and successfully applied in the pharmacokinetics study of vilazodone in rat. [ABSTRACT FROM AUTHOR]

Highlights: [•] The ex vivo stability of bilobalide was investigated for the first time. [•] Effective strategies to stabilize bilobalide in rat blood and plasma were developed. [•] An LC–MS/MS method for determining bilobalide in rat plasma was fully validated. [•] An LOQ of 5.0ng/mL was achieved with consumption of only 20μL of plasma. [ABSTRACT FROM AUTHOR]

Highlights: [•] We develop an assay method for mesoridazine in rat plasma using LC–MS/MS. [•] We develop a simple, rapid, and sensitive method by simple protein precipitation. [•] This assay variability limits set forth in the FDA guidelines. [•] The present method can be applied to pharmacokinetic and/or toxicokinetic studies. [Copyright &y& Elsevier]

Highlights: [•] A LC–MS/MS method was first developed and validated for the determination of deoxypodophyllotoxin in rat plasma. [•] Good peak shape and sensitivity with acceptable matrix effect could be obtained. [•] It is the first pharmacokinetic study of the intravenous administration of DPT in rats. [•] The pharmacokinetic parameters were obtained through two-compartment intravenous models analysis. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed and validated a novel quantification method using HPLC–MS/MS. [•] It is for the first time we simultaneous determined six main steroidal saponins in Paris polyphylla in vivo. [•] We report the pharmacokinetics parameters of steroidal saponins in rat for the first time. [•] We report the steroidal saponins have a long MRT and low concentration. [•] We introduced the Accelerated Solvent Extraction in sample preparation. [ABSTRACT FROM AUTHOR]

Highlights: [•] LC–ESI-MS/MS utilized for PK study of five phenolic components and paeoniflorin in Cerebralcare granule®. [•] The assay simultaneously determines five phenolic components and paeoniflorin in rat plasma. [•] LLOQs of these six active components are below 5.0ng/ml. [•] This is the first pharmacokinetic study of multiple components in Cerebralcare granule®. [ABSTRACT FROM AUTHOR]

Abstract: A simple, sensitive and specific liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for the quantification of milnacipran (MC) in rat plasma by using the liquid–liquid extraction method. Milnacipran-d10 (MCD10) was used as an internal standard (IS). Chromatographic separation was achieved on Zorbax SB-CN (4.6mm×75mm, 3.5µm) column with an isocratic mobile phase composed of 10mM ammonium acetate (pH 4.0) and methanol in the ratio of 25:75(v/v), at a flow-rate of 0.7mL/min. MC and MCD10 were detected with proton adducts at m/z 247.2→230.3 and m/z 257.2→240.4 in multiple reaction monitoring (MRM) positive mode respectively. The method was validated over a linear concentration range of 1.00–400.00ng/mL with a correlation coefficient (r 2)≥0.9850. This method demonstrated intra- and inter-day precision within 5.40–10.85% and 4.40–8.29% and accuracy within 97.00–104.20% and 101.64–106.23%. MC was found to be stable throughout three freeze–thaw cycles, bench top and postoperative stability studies. This method was successfully applied to a pharmacokinetic study of rats through i.v. administration. [Copyright &y& Elsevier]

Highlights: [•] We developed and validated a novel LC–MS/MS method for imperialine quantification. [•] The method debuted on pharmacokinetic study of imperialine in rats. [•] Pharmacokinetic study was done at low doses (mg/kg, i.v., 5; p.o., 1, 5 and 10). [•] Oral bioavailability of 3 p.o. groups was 31.2%, 53.6% and 47.4%, respectively. [Copyright &y& Elsevier]

Abstract: Bergenin, a C-glucoside of 4-O-methyl gallic acid from Bergenia purpurascens, is a naturally antitussive and expectorant agent. A rapid and sensitive liquid chromatography tandem mass spectrometry (LC–MS/MS) method has been developed and validated for the determination of the active component—bergenin, in rat plasma after oral administration of aqueous B. purpurascens extract. The plasma samples were pretreated by protein precipitation with acetonitrile and chromatographic separation was achieved on a Diamonsil® C18 column (150mm×4.6mm, 5μm) with isocratic elution using a mobile phase consisting of water–methanol (30:70, v/v) at a flow rate of 0.6mL/min. The detection was accomplished by a triple-quadrupole tandem mass spectrometer in multiple-reaction monitoring (MRM) scanning via an electrospray ionization (ESI) source operating in the negative mode. The optimized mass transition ion-pairs (m/z) for quantitation were 327.3/192.0 for bergenin, and 431.1/311.1 for IS. The time for each analysis run was only 3.5min between injections. The calibration curve exhibited good linearity (r 2>0.99) over a range of 1.00–2000ng/mL for bergenin. The lower limit of quantitation (LLOQ) was 1.00ng/mL. The intra- and inter-day precisions were no more than 11.8%, and relative errors (RE) were within the range of 0.0–4.4%. The validated method was successfully applied to investigate the pharmacokinetics of bergenin after oral administration of B. purpurascens extract in rats. [Copyright &y& Elsevier]

Highlights: [•] A sensitive and reliable LC–MS/MS method for analysis of berbamine in rat plasma is developed for the first time. [•] The LLOQ of this assay was 1ng/mL, which was lower than ever before (750ng/mL). [•] The method was fully validated and successfully applied to a pharmacokinetic study of berbamine in rats. [•] The pharmacokinetic parameters of berbamine in this paper are reported for the first time. [Copyright &y& Elsevier]

A rapid sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for determination of timosaponin AIII (TA-III) in rat plasma, using ginsenoside Re as an internal standard (IS). TA-III and the IS were detected in MRM mode with a negative ionization electrospray mass spectrometer. The calibration curves were linear over the concentration ranges from 11.14 to 1114 ng/mL and the lower limit of quantification (LLOQ) was 11.14 ng/mL. Intra-day and inter-day precisions (RSD) were within 10%, and accuracy ranged from 6.4% to 9.1%. The extraction recovery at three concentrations ranged from 92.3% to 95.5%. The validated method was successfully applied to monitor the concentrations of TA-III in rat plasma after intragastric administration. The best fit pharmacokinetic model to estimate the pharmacokinetic parameters was a single compartment model with weight of 1/x2 for oral administration groups of rats for TA-III. [ABSTRACT FROM AUTHOR]

A highly selective and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of scicinib, a novel thiosemicarbazone analogue and anticancer agent in rat plasma. Protein precipitation with saturated EDTA solution and methanol was selected for sample preparation, and brodimoprim was employed as the internal standard (IS). The analytes were separated on a Symmetry C18column (200 × 4.6 mm i.d., 5 µm) by isocratic elution with a mobile phase consisting of methanol and 0.2 mM EDTA (75:25, v/v) at a flow rate of 0.4 mL/min. After electrospray ionization, the analyte and IS were recorded under selected reaction monitoring (SRM) mode. The chosen transition wasm/z313.0 → 267.9 for scicinib andm/z339.0 → 280.9 for IS, respectively. The validated linearity range is 5–5000 ng/mL, with the lower limit of quantitation of 5 ng/mL. The developed method was successfully applied to a pharmacokinetic study of scicinib in rats after a single intravenous administration of 5 mg/kg. [ABSTRACT FROM AUTHOR]

Abstract: A novel, simple, and sensitive method for the determination of jujuboside A in rat plasma using liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) was developed. Following solid-phase extraction, measurement of jujuboside A was performed by negative ion electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode. The limit of detection was 1.25ng/mL, and the lower limit of quantification was 5ng/mL in rat plasma. Good linearity was obtained over the range of 6.25–500ng/mL, and the correlation coefficient was better than 0.998. The intra- and inter-day precisions ranged 4.4–7.5% and 2.9–10.7%, respectively. The accuracy derived from QC samples ranged 3.2–7.8% and 2.2–3.5%, respectively. The recovery ranged from 72.9 to 75.1% and the matrix effect from 96.7 to 105.3%. The analyte was stable under various conditions (at room temperature, during freeze–thaw, in the autosampler and under deep-freeze conditions). The developed method was successfully applied to the pharmacokinetic study in rats. [Copyright &y& Elsevier]

Abstract: Decitabine is chemically unstable at physiological temperature and pH. In addition, the bioanalysis of decitabine is easily interfered by endogenous 2-deoxycytidine. A simple, sensitive and specific LC–MS/MS method was developed for the analysis of decitabine in rat plasma. No exogenous stabilizers were used to prevent the degradation of decitabine in rat plasma. After deproteinized with acetonitrile at room temperature, rat plasma samples were analyzed on a Hypersil APS-2 NH2 column interfaced with a triple quadrupole tandem mass spectrometer in positive electrospray ionization mode. Decitabine was completely separated from 2-deoxycytidine using gradient elution of water (solvent A) and acetonitrile (solvent B) at a flow rate of 1mL/min. To quantify decitabine and daidzin (internal standard), respectively, multiple reaction monitoring (MRM) transitions of m/z 251.1→134.7 and m/z 417.3→255.3 was performed. The assay was linear over the concentration range of 5.0–2000ng/mL. The intra- and inter-day precision was within 12.0% in terms of relative standard deviation (RSD%) and the accuracy within 5.9% in terms of relative error. The LC–MS/MS method was fully validated for its sensitivity, selectivity, stability study, matrix effect and recovery. The data indicate that this LC–MS/MS method is a specific and effective method for the pharmacokinetic study of decitabine in rat plasma. Compared with the previously reported analytical methods, this method showed easy and economic sample preparation, good specificity and high sensitivity with less plasma (50μL). [Copyright &y& Elsevier]

Abstract: TM-25659 compound, a novel TAZ modulator, is developed for the control of bone loss and obesity. TAZ is known to bind to a variety of transcription factors to control cell differentiation and organ development. A selective and sensitive method was developed for the determination of TM-25659 concentrations in rat plasma. The drug was measured by liquid chromatography–tandem mass spectrometry after liquid–liquid extraction with ethyl acetate. TM-25659 and the internal standard imipramine were separated on a Hypersil GOLD C18 column with a mixture of acetonitrile–ammonium formate (10mM) (90:10, v/v) as the mobile phase. The ions m/z 501.2→207.2 for TM-25659 and m/z 281.0→86.0 for imipramine in multiple reaction monitoring mode were used for the quantitation. The calibration range was 0.1–100μg/ml with a correlation coefficient greater than 0.99. The lower limit of quantitation of TM-25659 in rat plasma was 0.1μg/ml. The percent recoveries of TM-25659 and imipramine were 98.6% and 95.7% from rat plasma, respectively. The intra- and inter-batch precisions were 3.17–15.95% and the relative error was 0.38–10.82%. The developed assay was successfully applied to a pharmacokinetic study of TM-25659 administered intravenously (10mg/kg) to rats. [Copyright &y& Elsevier]

Abstract: A simple, rapid and sensitive method for the determination of geniposidic acid (GSA) in rat plasma was developed using liquid chromatography tandem mass spectrometry (LC–MS/MS). Geniposide (GS) was used as the internal standard. Rat plasma pretreated by solid-phase extraction (SPE) was analyzed by LC–MS/MS with negative ion mode electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. The analytical column was C8 column and the mobile phase was methanol (A) and water (B). The flow rate was set at 0.8mL/min with split ratio of 1:3, the total run time was 15min. The MS/MS ion transitions monitored were m/z 373.3–211.1 for GSA and m/z 387.3–225.3 for GS. The quantification limit was 5ng/mL within a linear range of 10–4000ng/mL. The inter-day and intra-day accuracy and precision were within ±10%. The method was fully validated for its sensitivity, selectivity, matrix effect, stability study and recovery. The data indicate that our LC–MS/MS assay is an effective method for the pharmacokinetics study of GSA in rat plasma. [Copyright &y& Elsevier]