A rapid and sensitive determination of hypoxic radiosensitizer agent nimorazole in rat plasma by LC‐MS/MS and its application to a pharmacokinetic study

A highly sensitive, accurate and robust LC‐MS/MS method was developed and validated for determination of nimorazole (NMZ) in rat plasma using metronidazole (MNZ) as internal standard (IS). The analyte and IS were extracted from plasma by precipitating protein with acetonitrile and were chromatographed using an Agilent Poroshell 120, EC‐C₁₈ column. The mobile phase was composed of a mixture of acetonitrile and 0.1 % formic acid (85:15 v/v). The total run time was 1.5 min and injection volume was 5 μL. Multiple reaction monitoring mode using the transitions of m/z 227.1 → m/z 114.0 for MNZ and m/z 172.10 → m/z 128.1 for IS were monitored on a triple quadrupole mass spectrometer, operating in positive ion mode. The calibration curve was linear in the range of 0.25–200 ng/mL (r² > 0.9996) and the lower limit of quantification was 0.25 ng/mL in the rat plasma samples. Recoveries of NMZ ranged between 88.05 and 95.25%. The precision (intra‐day and inter‐day) and accuracy of the quality control samples were 1.25–8.20% and ?2.50–3.10, respectively. The analyte and IS were found to be stable during all sample storage and analysis procedures. The LC‐MS/MS method described here was validated and successfully applied to pharmacokinetic study in rats. Copyright © 2015 John Wiley & Sons, Ltd.     

A validated LC‐MS/MS assay for simultaneous quantification of methotrexate and tofacitinib in rat plasma: application to a pharmacokinetic study

A highly sensitive, specific and rapid LC‐ESI‐MS/MS method has been developed and validated for simultaneous quantification of methotrexate (MTX) and tofacitinib (TFB) in rat plasma (50 μL) using phenacetin as an internal standard (IS), as per the US Food and Drug Administration guidelines. After a solid‐phase extraction procedure, the separation of the analytes and IS was performed on a Chromolith RP_18e column using an isocratic mobile phase of 5 m m ammonium acetate (pH 5.0) and acetonitrile at a ratio of 25:75 (v/v) using flow‐gradient with a total run time of 3.5 min. The detection was performed in multiple reaction monitoring mode, using the transitions of m/z 455.2 → 308.3, m/z 313.2 → 149.2 and m/z 180.3 → 110.2 for MTX, TFB and IS, respectively. The calibration curves were linear over the range of 0.49–91.0 and 0.40–74.4 ng/mL for MTX and TFB, respectively. The intra‐ and interday accuracy and precision values for MTX and TFB were <15% at low quality control (QC), medium QC and high QC and <20% at lower limit of quantification. The validated assay was applied to derive the pharmacokinetic parameters for MTX and TFB post‐dosing of MTX and TFB orally and intravenously to rats. Copyright © 2014 John Wiley & Sons, Ltd.     

LC–ESI–MS/MS determination of copanlisib,a novel PI3K inhibitor,in mouse plasma and its application to a pharmacokinetic study in mice

A sensitive, selective and rapid LC–ESI–MS/MS method has been developed and validated for the quantification of copanlisib in mouse plasma using enasidenib as an internal standard (IS) as per regulatory guideline. Copanlisib and the IS were extracted from mouse plasma using ethyl acetate as an extraction solvent and chromatographed using an isocratic mobile phase (0.2% formic acid–acetonitrile; 25:75, v/v) on a HyPURITY C₁₈ column. Copanlisib and the IS eluted at ~0.95 and 2.00 min, respectively. The MS/MS ion transitions monitored were m/z 481.1 → 360.1 and m/z 474.0 → 456.0 for copanlisib and the IS, respectively. The calibration range was 3.59–3588 ng/mL. The intra‐ and inter‐batch accuracy and precision (RE and RSD) across quality controls met the acceptance criteria. Stability studies showed that copanlisib was stable in mouse plasma for one month. This novel method has been applied to a pharmacokinetic study in mice.     

Development and validation of an LC‐ESI‐MS/MS method for the quantitation of hemslecin A in rhesus monkey plasma and its application in pharmacokinetics

In this study, a new LC‐ESI‐MS/MS‐based method was validated for the quantitation of hemslecin A in rhesus monkey plasma using otophylloside A as internal standard (IS). Hemslecin A and the IS were extracted from rhesus monkey plasma using liquid–liquid extraction as the sample clean‐up procedure, and were subjected to chromatography on a Phenomenex Luna CN column (150 × 2.0 mm, 3.0 µm) with the mobile phase consisting of methanol and 0.02 mol/mL ammonium acetate (55:45, v/v) at a flow rate of 0.2 mL/min. Detection was performed on an Agilent G6410B tandem mass spectrometer by positive ion electrospray ionization in multiple reaction monitoring mode, monitoring the transitions m/z 580.5 [M + NH₄]⁺ → 503.4 and m/z 518.2 [M + NH₄]⁺ → 345.0 for hemslecin A and IS, respectively. The assay was linear over the concentration range of 0.5–200 ng/mL and was successfully applied to a pharmacokinetic study in rhesus monkeys. Copyright © 2013 John Wiley & Sons, Ltd.     

A simple and sensitive LC‐MS/MS method for the determination of sotalol in rat plasma

A sensitive, rapid and robust HPLC method with tandem mass spectrometry (HPLC/MS/MS) detection has been developed and validated for the quantification of sotalol in rat plasma. Plasma samples were precipitated with acetonitrile before analysis. The chromatographic separation was performed on an Atlantis hydrophilic interaction liquid chromatography Silica column (50 × 2.1 mm, 3 µm) with a gradient mobile phase of 10 mm NH₄COOH (containing 0.2% of formic acid) as buffer A and acetonitrile as mobile phase B. Sotalol (m/z 273.2 → 255.1) and atenolol (the internal standard, IS, m/z 267.2 → 190.1) were monitored under positive ionization mode with 5500 QTRAP. Retention time of sotalol and the IS were 2.69 and 3.43 min, respectively. The linear range was 5–500 nm based on the analysis of 0.1 mL of plasma. The intrabatch precision ranged from 1.2 to 6.1%, and the inter‐batch precision was from 3.3 to 6.5%. The coefficient of variation of IS‐normalized matrix factor was 7.6%. Experiments for stability were performed and the analyte was sufficiently stable. A run time of 6 min for each injection made it possible to analyze a high throughput of plasma samples. The assay was successfully applied to the determination of sotalol in rat plasma after a micro‐dose oral administration. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of tigecycline in human plasma by LC–MS/MS and its application to population pharmacokinetics study in Chinese patients with hospital‐acquired pneumonia

A selective, sensitive and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the determination of tigecycline (TGC) in human plasma, using tigecycline‐d₉ as an internal standard (IS). Analytical samples were prepared using a protein precipitation method coupled with a concentration process. The analyte and IS were separated on a reversed‐phase Waters Acquity UPLC^® BEH‐C₁₈ column (2.1 × 50 mm i.d., 1.7 μm) with a flow rate of 0.25 mL/min. The mobile phase consisted of water, containing 0.2% formic acid (v/v) with 10 mm ammonium formate (A) and acetonitrile (B). The mass spectrometer was operated in selected reaction monitoring mode through electrospray ionization ion mode using the transitions of m/z 586.2 → 513.1 and m/z 595.1 → 514.0 for TGC and IS, respectively. The linearity of the method was in the range of 10–5000 ng/mL. Intra‐ and inter‐batch precision (CV) for TGC was <9.27%, and the accuracy ranged from 90.06 to 107.13%. This method was successfully applied to the analysis of samples from hospital‐acquired pneumonia patients treated with TGC, and a validated population pharmacokinetic model was established. This developed method could be useful to predict pharmacokinetics parameters and valuable for further pharmacokinetics/pharmacodynamics studies.     

Development and validation of UHPLC‐MS/MS assay for rapid determination of a carvone Schiff base of isoniazid (CSB‐INH) in rat plasma: application to pharmacokinetic study

In this study, a fast UHPLC‐MS/MS method was developed and validated for the determination of a novel potent carvone Schiff base of isoniazid (CSB‐INH) in rat plasma using carbamazepine as an internal standard (IS). After a single‐step protein precipitation by acetonitrile, CSB‐INH and IS were separated on an Acquity BEH^TM C₁₈ column (50 × 2.1 mm, 1.7 µm) under an isocratic mobile phase, consisting of acetonitrile: 10 mM ammonium acetate (95:5, v/v), at a flow rate of 0.3 mL/min. Quantification was performed on a triple quadrupole tandem mass spectrometer in multiple reactions monitoring mode by using positive electrospray ionization source. The precursor to product ion transitions were set at m/z 270.08 → 79.93 for CSB‐INH and m/z 237.00 → 178.97 for IS. The proposed method was validated in compliance with US Food and Drug Administration and European Medicines Agency guidelines for bioanalytical method validation. The method was found to be linear in the range of 0.35–2500 ng/mL (r² ≥ 0.997) with a lower limit of quantification of 0.35 ng/mL. The intra‐ and inter‐day precision values were ≤12.0% whereas accuracy values ranged from 92.3 to 108.7%. In addition, other validation results were within the acceptance criteria and the method was successfully applied in a pharmacokinetic study of CSB‐INH in rats. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of 9‐dehydro‐17‐hydro‐andrographolide and sodium 9‐dehydro‐17‐hydro‐andrographolide‐19‐yl sulfate in rat plasma by UHPLC‐ESI‐MS/MS after administration of xiyanping injection: application to a pharmacokinetic study

9‐Dehydro‐17‐hydro‐andrographolide (DHA) and sodium 9‐dehydro‐17‐hydro‐andrographolide‐19‐yl sulfate (DHAS) are active ingredients of xiyanping injection in clinical use. A simple, rapid and sensitive UHPLC‐ESI‐MS/MS method was developed for the determination of DHA and DHAS in rat plasma, and the pharmacokinetics of DHA and DHAS after intravenous administration of xiyanping injection was investigated. The plasma samples were treated with methanol to precipitate out protein, and the separation of DHA and DHAS was achieved on a Waters BEH C₁₈ column with a mobile phase consisting of acetonitrile and 10 mmol/L ammonium acetate solution at a flow rate of 0.4 mL/min. DHA, DHAS and the internal standard (internal standard, IS) diethylstilbestrol were detected at negative ion mode. The precursor‐product ion pairs used in multiple reaction monitoring mode were: m/z 349.1 → 286.9 (DHA), m/z 428.9 → 96.0 (DHAS) and m/z 267.1 → 236.9 (IS). Calibration curves offered satisfactory linearity within the test range, and all correlation coefficients were >0.995. The lower limit of detection of DHA and DHAS in plasma samples were determined to be 0.1 ng/mL. The lower limit of quantitation was 0.5 ng/mL for DHA and DHAS. All the recoveries of the quality control samples were in the range of 86.0–102.4%. The ratios of matrix effect were between 89.2 and 105.1%. The method was fully validated and successfully applied to the pharmacokinetic study of DHA and DHAS in rats. The study showed that both DHA and DHAS were distributed and eliminated rapidly in rats. Copyright © 2013 John Wiley & Sons, Ltd.     

A sensitive LC‐MS/MS method for the quantification of febuxostat in human plasma and its pharmacokinetic application

An improved, simple and highly sensitive LC‐MS/MS method has been developed and validated for quantification of febuxostat with 100 μL human plasma using febuxostat‐d₇ as an internal standard (IS) according to regulatory guidelines. The analyte and IS were extracted from human plasma via liquid–liquid extraction using diethyl ether. The chromatographic separation was achieved on a Zorbax C₁₈ column using a mixture of acetonitrile and 5 mm ammonium formate (60:40, v/v) as the mobile phase at a flow rate of 0.5 mL/min. The total run time was 5.0 min and the elution of febuxostat and IS occurred at 1.0 and 1.5 min, respectively. A linear response function was established for the range of concentrations 1–6000 ng/mL (r > 0.99). The precursor to product ion transitions monitored for febuxostat and IS were m/z 317.1 → 261.1 and 324.2 → 262.1, respectively. The intra‐ and inter‐day precisions (%RSD) were within 1.29–9.19 and 2.85–7.69%, respectively. The proposed method was successfully applied to pharmacokinetic studies in humans. Copyright © 2013 John Wiley & Sons, Ltd.     

Development and validation of a highly sensitive LC‐MS/MS‐ESI method for the determination of bicalutamide in mouse plasma: application to a pharmacokinetic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of bicalutamide in mouse plasma using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the negative‐ion mode. The assay procedure involves extraction of bicalutamide and tolbutamide (internal standard, IS) from mouse plasma with a simple protein precipitation method. Chromatographic separation was achieved using an isocratic mobile phase (0.2% formic acid:acetonitrile, 35:65, v/v) at a flow rate of 0.5 mL/min on an Atlantis dC₁₈ column (maintained at 40 ± 1°C) with a total run time of 3.0 min. The MS/MS ion transitions monitored were m/z 428.9 → 254.7 for bicalutamide and m/z 269.0 → 169.6 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 1.04 ng/mL and the linearity range extended from 1.04 to 1877 ng/mL. The intra‐ and inter‐day precisions were in the ranges of 0.49–4.68 and 2.62–4.15, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Rapid determination of losartan and losartan acid in human plasma by multiplexed LC–MS/MS

A rapid LC–MS/MS method has been developed and validated for the determination of losartan (LOS) and its metabolite losartan acid (LA) (EXP‐3174) in human plasma using multiplexing technique (two HPLC units connected to one MS/MS). LOS and LA were extracted from human plasma by SPE technique using Oasis HLB® cartridge without evaporation and reconstitution steps. Hydroflumethiazide (HFTZ) was used as an internal standard (IS). The analytes were separated on Zorbax SB C‐18 column. The mass transition [M–H] ions used for detection were m/z 421.0 → 127.0 for LOS, m/z 435.0 → 157.0 for LA, and m/z 330.0 → 239.0 for HFTZ. The proposed method was validated over the concentration range of 2.5–2000 ng/mL for LOS and 5.0–3000 ng/mL for LA with correlation coefficient ?0.9993. The overall recoveries for LOS, LA, and IS were 96.53, 99.86, and 94.16%, respectively. Total MS run time was 2.0 min/sample. The validated method has been successfully used to analyze human plasma samples for applications in 100 mg fasted and fed pharmacokinetic studies.     

Development and validation of a sensitive and high‐throughput LC‐MS/MS method for the simultaneous determination of esomeprazole and naproxen in human plasma

A sensitive and high‐throughput LC‐MS/MS method has been developed and validated for the combined determination of esomeprazole and naproxen in human plasma with ibuprofen as internal standard. Solid‐phase extraction was used to extract both analytes and internal standard from human plasma. Chromatographic separation was achieved in 4.0 min on XBridge C₁₈ column using acetonitrile–25 mM ammonium formate (70:30, v/v) as mobile phase. Mass detection was achieved by ESI/MS/MS in negative ion mode, monitoring at m/z 344.19 → 194.12, 229.12 → 169.05 and 205.13 → 161.07 for esomeprazole, naproxen and IS, respectively. The calibration curves were linear from 3.00 to 700.02 ng/mL for esomeprazole and 0.50 to 150.08 ng/mL for naproxen. The intra‐ and inter‐batch precision and accuracy across four quality control levels met established criteria of US Food and Drug Administration guidelines. The assay is suitable for measuring accurate esomeprazole and naproxen plasma concentrations in human bioequivalence study following combined administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination and validation of hupehenine in rat plasma by UPLC‐MS/MS and its application to pharmacokinetic study

In this work, a sensitive and selective ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method for determination of hupehenine in rat plasma was developed and validated. After addition of imperialine as an internal standard (IS), protein precipitation by acetonitrile–methanol (9:1, v/v) was used to prepare samples. Chromatographic separation was achieved on a UPLC BEH C₁₈ column (2.1 × 100 mm, 1.7 µm) with 0.1% formic acid and acetonitrile as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reaction monitoring mode was used for quantification using target fragment ions m/z 416.3 → 98.0 for hupehenine, and m/z 430.3 → 138.2 for IS. Calibration plots were linear throughout the range 2–2000 ng/mL for hupehenine in rat plasma. Mean recoveries of hupehenine in rat plasma ranged from 92.5 to 97.3%. Relative standard deviations of intra‐day and inter‐day precision were both <6%. The accuracy of the method was between 92.7 and 107.4%. The method was successfully applied to a pharmacokinetic study of hupehenine after either oral or intravenous administration. For the first time, the bioavailability of hupehenine was reported as 13.4%. Copyright © 2015 John Wiley & Sons, Ltd.     

Development and validation of a sensitive LC–MS/MS assay for quantification of bruceine D in rat plasma

A sensitive LC–MS/MS method for the determination of bruceine D in rat plasma was developed. The analyte and IS were separated on a Luna C₁₈ column (2.1 × 50 mm, 1.7 μm) using a mobile phase of acetonitrile and 0.1% formic acid in water (40:60, v/v) at a flow rate of 0.25 mL/min. The selected reaction monitoring mode was chosen to monitor the precursor‐to‐product ion transitions of m/z 409.2 → 373.2 for bruceine D and m/z 469.2 → 229.3 for IS using a negative ESI mode. The method was validated over a concentration range of 0.5–2000 ng/mL for bruceine D. Total chromatography time for each run was 3.5 min. The method was successfully applied to a pharmacokinetic study of bruceine D in rats. Copyright © 2016 John Wiley & Sons, Ltd.     

A UPLC–MS/MS method for comparative pharmacokinetics study of morusin and morin in normal and diabetic rats

The aim of this study was to establish and validate a rapid, selective and reliable ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) for simultaneous quantitations of morin and morusin, and to investigate their pharmacokinetics difference between normal and diabetic rats after oral administration. Plasma samples were pretreated via protein precipitation with acetonitrile. Genkwanin was used as internal standard (IS). Analytes and IS were separated on a Thermo Hypersil Gold C₁₈ column (50 × 4.6 mm, 3 μm) using gradient elution. The mobile phase consisted of acetonitrile and 0.1% formic acid in water at a flow rate of 0.5 mL/min. Mass spectrometry detection was carried out by means of negative electrospray ionization source and multipe‐reaction monitoring mode. The transitions of m/z 300.9 → 151.2 for morin, m/z 419.2 → 297.1 for morusin and m/z 283.1 → 268.2 for IS were chosen for quantification. Calibration curves were linear in the range of 1.01–504.2 ng/mL (r² ≥ 0.99) for morin and 1.02–522.3 ng/mL (r² ≥ 0.99) for morusin. The lower limit of quantification was 1.02 ng/mL for morin and 1.05 ng/mL for morusin. The extraction recovery was >85.1% for each analyte. No obvious matrix effect was observed under the present UPLC–MS/MS conditions during all of the bioanalysis. The stability study demonstrated that morin and morusin remained stable during the whole analytical procedure. The method was successfully applied to support the pharmacokinetic comparisons of morin and morusin between normal and diabetic rats.     

Determination of docetaxel in rat plasma and its application in the comparative pharmacokinetics of Taxotere and SID530, a novel docetaxel formulation with hydroxypropyl‐β‐cyclodextrin

In this study, a sensitive, simple and reliable method for the quantification of docetaxel in rat plasma was developed and validated using liquid chromatography–tandem mass spectrometry (LC‐MS/MS). The plasma samples were prepared by protein precipitation, and paclitaxel was used as an internal standard (IS). Chromatographic separation was achieved using a Gemini C₁₈ column (2.0 × 150 mm, 5 µm) with a mobile phase consisting of 0.1% formic acid–acetonitrile (30:70, v/v). The precursor–product ion pairs used for multiple reaction monitoring were m/z 808.5 → 527.5 (docetaxel) and m/z 854.2 → 286.5 (IS, paclitaxel). A calibration curve for docetaxel was constructed over the range 1–1000 ng/mL. The developed method was specific, precise and accurate, and no matrix effect was observed. The validated method was applied in a comparative pharmacokinetic study in which two docetaxel formulations, SID530, a new parenteral formulation of docetaxel with hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD), and Taxotere, were administered to rats at a dose of 5 mg/kg. For SID530 and Taxotere, the mean C₀ values were 1494 and 1818 ng/mL, respectively, and the AUC_last values were 837 and 755 h ng/mL, respectively. These two formulations did not show any statistical differences with regard to the pharmacokinetic parameters, thus establishing that the SID530 and Taxotere products are pharmacokinetically comparable in male rats. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of an LC‐MS/MS method for the determination of a novel thienoquinolin urea transporter inhibitor PU‐48 in rat plasma and its application to a pharmacokinetic study

A specific, sensitive and stable high‐performance liquid chromatographic–tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the quantitative determination of methyl 3‐amino‐6‐methoxythieno [2,3‐b]quinoline‐2‐carboxylate (PU‐48), a novel diuretic thienoquinolin urea transporter inhibitor in rat plasma. In this method, the chromatographic separation of PU‐48 was achieved with a reversed‐phase C₁₈ column (100 × 2.1 mm, 3 μm) at 35°C. The mobile phase consisted of acetonitrile and water with 0.05% formic acid added with a gradient elution at flow rate of 0.3 mL/min. Samples were detected with the triple‐quadrupole tandem mass spectrometer with multiple reaction monitoring mode via electrospray ionization source in positive mode. The retention time were 6.2 min for PU‐48 and 7.2 min for megestrol acetate (internal standard, IS). The monitored ion transitions were mass‐to‐charge ratio (m/z) 289.1 → 229.2 for PU‐48 and m/z 385.3 → 267.1 for the internal standard. The calibration curve for PU‐48 was linear over the concentration range of 0.1–1000 ng/mL (r² > 0.99), and the lower limit of quantitation was 0.1 ng/mL. The precision, accuracy and stability of the method were validated adequately. The developed and validated method was successfully applied to the pharmacokinetic study of PU‐48 in rats.     

A quantitative determination of fluorochloridone in rat plasma by UPLC‐MS/MS method: application to a pharmacokinetic study

A precise, high‐throughput and sensitive ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method has been developed for the determination of fluorochloridone (FLC) in rat plasma. The extraction of analytes from plasma samples was carried out by protein precipitation procedure using acetonitrile prior to UPLC‐MS/MS analysis. Verapamil was proved as a proper internal standard (IS) among many candidates. The chromatographic separation based on UPLC was well optimized. Multiple reaction monitoring in positive electrospray ionization was used with the optimized MS transitions at: m/z 312.0 → 292.0 for FLC and m/z 456.4 → 165.2 for IS. This method was well validated with good linear response (r² > 0.998) observed over the investigated range of 3–3000 ng/mL and with satisfactory stability. This method was also characterized with adequate intra‐ and inter‐day precision and accuracy (within 12%) in the quality control samples, and with high selectivity and less matrix effect observed. Total running time was only 1.5 min. This method has been successfully applied to a pilot FLC pharmacokinetic study after oral administration. Copyright © 2016 John Wiley & Sons, Ltd.     

Simultaneous quantification of metformin and glipizide in human plasma by high‐performance liquid chromatography–tandem mass spectrometry and its application to a pharmacokinetic study

A selective, sensitive and rapid high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS) method was developed and validated to determine metformin and glipizide simultaneously in human plasma using phenacetin as internal standard (IS). After one‐step protein precipitation of 200 μL plasma with methanol, metformin, glipizide and IS were separated on a Kromasil Phenyl column (4.6 × 150 mm, 5 µm) at 40°C with an isocratic mobile phase consisting of methanol–10 mmol/L ammonium acetate (75:25, v/v) at a flow rate of 0.35 mL/min. Electrospray ionization source was applied and operated in the positive mode. Multiple reaction monitoring using the precursor → product ion combinations of m/z 130 → m/z 71, m/z 446 → m/z 321 and m/z 180 → m/z 110 were used to quantify metformin, glipizide and IS, respectively. The linear calibration curves were obtained over the concentration ranges 4.10–656 ng/mL for metformin and 2.55–408 ng/mL for glipizide. The relative standard deviation of intra‐day and inter‐day precision was below 10% and the relative error of accuracy was between ?7.0 and 4.6%. The presented HPLC‐MS/MS method was proved to be suitable for the pharmacokinetic study of metformin hydrochloride and glipizide tablets in healthy volunteers after oral administration. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and application of a LC–MS/MS assay for the simultaneous quantification of edaravone and taurine in beagle plasma

An LC–MS/MS method was developed and validated for the simultaneous quantification of edaravone and taurine in beagle plasma. The plasma sample was deproteinized using acetonitrile containing formic acid. Chromatographic separations were achieved on an Agilent Zorbax SB‐Aq (100 × 2.1 mm, 3.5 μm) column, with a gradient of water (containing 0.03% formic acid) and methanol as the mobile phase at a flow rate of 0.3 mL/min. The analyte detection was carried out in multiple reaction monitoring mode and the optimized precursor‐to‐product transitions of m/z [M+H]⁺ 175.1 → 133.0 (edaravone), m/z [M+H]⁺ 189.1 → 147.0 (3‐methyl‐1‐p‐tolyl‐5‐pyrazolone, internal standard, IS), m/z [M–H]^? 124.1→80.0 (taurine), and m/z [M–H]^? 172.0 → 80.0 (sulfanilic acid, IS) were employed to quantify edaravone, taurine, and their corresponding ISs, respectively. The LOD and the lower LOQ were 0.01 and 0.05 μg/mL for edaravone and 0.66 and 2 μg/mL for taurine, respectively. The calibration curves of these two analytes demonstrated good linearity (r ＞ 0.99). All the validation data including the specificity, precision, recovery, and stability conformed to the acceptable requirements. This validated method has successfully been applied in the pharmacokinetic study of edaravone and taurine mixture in beagle dogs.