Development and validation of a sensitive UHPLC‐MS/MS method for the simultaneous analysis of tramadol,dextromethorphan chlorpheniramine and their major metabolites in human plasma in forensic context: application to pharmacokinetics

The prerequisites for forensic confirmatory analysis by LC/MS/MS with respect to European Union guidelines are chromatographic separation, a minimum number of two MS/MS transitions to obtain the required identification points and predefined thresholds for the variability of the relative intensities of the MS/MS transitions (MRM transitions) in samples and reference standards. In the present study, a fast, sensitive and robust method to quantify tramadol, chlorpheniramine, dextromethorphan and their major metabolites, O‐desmethyltramadol, dsmethyl‐chlorpheniramine and dextrophan, respectively, in human plasma using ibuprofen as internal standard (IS) is described. The analytes and the IS were extracted from plasma by a liquid–liquid extraction method using ethyl acetate–diethyl‐ether (1:1). Extracted samples were analyzed by ultra‐high‐performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (UHPLC‐ESI‐MS/MS). Chromatographic separation was performed by pumping the mobile phase containing acetonitrile, water and formic acid (89.2:11.7:0.1) for 2.0 min at a flow rate of 0.25 μL/min into a Hypersil‐Gold C₁₈ column, 20 × 2.0 mm (1.9 µm) from Thermoscientific, New York, USA. The calibration curve was linear for the six analytes. The intraday precision (RSD) and accuracy (RE) of the method were 3–9.8 and ?1.7–4.5%, respectively. The analytical procedure herein described was used to assess the pharmacokinetics of the analytes in 24 healthy volunteers after a single oral dose containing 50 mg of tramadol hydrochloride, 3 mg chlorpheniramine maleate and 15 mg of dextromethorphan hydrobromide. Copyright © 2014 John Wiley & Sons, Ltd.     

Development and validation of a UHPLC‐MS/MS bioanalytical method to quantify in plasma the analgesic candidate PT‐31 following a preliminary pharmacokinetic study in rats

A selective and sensitive UHPLC‐MS/MS bioanalytical method to determine PT‐31, an analgesic drug candidate, in rat plasma was developed and validated. Analyses were performed using a UHPLC‐MS/MS system equipped with an electrospray ionization interface operating in the positive ionization mode using a C₁₈ reversed‐phase column with a mobile phase of water:acetonitrile (68:31, v/v) containing 0.1% acetic acid eluting in a gradient mode with a flow rate of 0.3 mL/min. Plasma samples were deproteinized with cold acetonitrile containing 0.01% TFA (1:2, v/v) and 50 μL of the supernatant were injected into the system. PT‐31 and phenytoin (internal standard) retention times were roughly 1.0 and 1.5 min, respectively. Linear standard curves were plotted for the 0.01–10 µg/mL concentration range, with a coefficient of determination > 0.99. The method's precision was over 88%. Maximum intra‐ and inter‐day relative standard deviations were 14.6% and 11.6%, respectively. Interfering substances were not detected in the chromatogram, indicating that the method was specific. PT‐31 stability was assessed under different temperature and storage settings. The method was used to characterize PT‐31 plasma pharmacokinetics following administration of 5 mg/kg i.v. to Wistar rats. Therefore, the method described is sensitive, linear, precise and specific enough to determine PT‐31 in preclinical pharmacokinetic investigations. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous determination of sibutramine and its active metabolites in human plasma by LC‐MS/MS and its application to a pharmacokinetic study

A simple and sensitive liquid chromatography–electrospray ionization–tandem mass spectrometry (LC‐ESI‐MS/MS) technique was developed and validated for the determination of sibutramine and its N‐desmethyl metabolites (M1 and M2) in human plasma. After extraction with methyl t‐butyl ether, chromatographic separation of analytes in human plasma was performed using a reverse‐phase Luna C₁₈ column with a mobile phase of acetonitrile–10 mm ammonium formate buffer (50:50, v/v) and quantified by ESI‐MS/MS detection in positive ion mode. The flow rate of the mobile phase was 200 μL/min and the retention times of sibutramine, M1, M2 and internal standard (chlorpheniramine) were 1.5, 1.4, 1.3 and 0.9 min, respectively. The calibration curves were linear over the range 0.05–20 ng/mL, for sibutramine, M1 and M2. The lower limit of quantification was 0.05 ng/mL using 500 μL of human plasma. The mean accuracy and the precision in the intra‐ and inter‐day validation for sibutramine, M1 and M2 were acceptable. This LC‐MS/MS method showed improved sensitivity and a short run time for the quantification of sibutramine and its two active metabolites in plasma. The validated method was successfully applied to a pharmacokinetic study in human. Copyright © 2011 John Wiley & Sons, Ltd.     

Fast quantification of cyclophosfamide and its N‐dechloroethylated metabolite 2‐dechloroethylcyclophosphamide in human plasma by UHPLC‐MS/MS

A rapid, novel and reliable UHPLC‐MS/MS method was developed and validated for simultaneous determination of cyclophosphamide (CP) and its dechloroethylated metabolite, 2‐dechloroethylcyclosphamide (2‐DCECP) in human plasma. The plasma samples were conducted by protein precipitation with 3‐fold acetonitrile, containing 0.1% formic acid. Mass spectrometric detection was performed using electrospray positive ionization with multiple reaction monitoring mode, using tinidazole as internal standard (IS). Chromatographic separation was performed on an Agilent poroshell 120 SB‐C₁₈ column (2.1 × 75 mm, 2.7 µm) using gradient elution of acetonitrile and 0.1% formic acid at a flow rate of 0.5 mL/min, the total run time was 2.5 min. The limit of quantification (LOQ) was 20 ng/mL for both CP and 2‐DCECP. Accuracies and precisions were <15% at LOQ and below 10% at quality control concentration levels. This UHPLC‐MS/MS method was successfully applied for the estimation of CP and 2‐DCECP in human plasma, which was also useful for clinical toxicology studies and therapeutic drug monitoring of CP. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of calycosin‐7‐O‐β‐d‐glucoside,calycosin, formononetin,astragaloside IV and schisandrin in rat plasma by LC‐MS/MS: application to a pharmacokinetic study after oral administration of Shenqi Wuwei chewable tablets

A rapid, sensitive and reliable high‐performance liquid chromatography–mass spectrometry (LC‐MS/MS) method was developed and validated for simultaneous quantification of the five main bioactive components, calycosin, calycosin‐7‐O‐β‐d ‐glucoside, formononetin, astragaloside IV and schisandrin in rat plasma after oral administration of Shenqi Wuwei chewable tablets. Plasma samples were extracted using solid‐phase extraction separated on a CEC₁₈ column and detected by MS with an electrospray ionization interface in multiple‐reaction monitoring mode. Calibration curves offered linear ranges of two orders of magnitude with r > 0.995. The method had a lower limit of quantitation of 0.1, 0.02, 0.1, 1 and 0.1 ng/mL for calycosin, calycosin‐7‐O‐β‐d ‐glucoside, formononetin, astragaloside IV and schisandrin, respectively. Intra‐ and inter‐day precisions (relative standard deviation) for all analytes ranged from 0.97 to 7.63% and from 3.45 to 10.89%, respectively. This method was successfully applied to the pharmacokinetic study of the five compounds in rats after oral administration of Shenqi Wuwei chewable tablets. Copyright © 2014 John Wiley & Sons, Ltd.     

Qualitative and quantitative analysis of major constituents from Dazhu Hongjingtian capsule by UPLC/Q‐TOF‐MS/MS combined with UPLC/QQQ‐MS/MS

In this work, a sensitive and efficient method was established and validated for qualitative and quantitative analysis of major bioactive constituents in Dazhu Hongjingtian capsule by liquid chromatography tandem mass spectrometry. A total of 32 compounds were tentatively identified using ultra‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry. Furthermore, 12 constituents, namely gallic acid, 3,4‐dihydroxybenzoic acid, salidroside, p‐ coumaric acid‐4‐O ‐β ‐d ‐glucopyranoside, bergeninum, 4‐hydroxybenzoic acid, 4‐hydroxyphenylacetic acid, syringate, 6′′‐O ‐galloylsalidroside, rhodiosin, rhodionin and kaempferol‐7‐O ‐α ‐l ‐rhamnoside, were simultaneously quantified by the developed ultra‐performance liquid chromatography coupled with a triple quadrupole mass spectrometry method in 9 min. All of them were analyzed on an Agilent ZorBax SB‐C₁₈ column (3.0 × 100 mm, 1.8 μm) with linear gradient elution of methanol–0.1% formic acid water. The proposed method was applied to analyze three batches of samples with acceptable linearity (R , 0.9979–0.9997), precision (RSD, 1.3–4.7%), repeatability (RSD, 1.7–4.9%), stability (RSD, 2.2–4.9%) and recovery (RSD, 0.6–4.4%) of the 12 compounds. As a result, the analytical method possessing high throughput and sensitivity is suitable for the quality control of Dazhu Hongjingtian capsule.     

Development and validation of a robust LC‐MS‐MS with atmospheric pressure chemical ionization for quantitation of carbazochrome sodium sulfonate in human plasma: application to a pharmacokinetic study

A highly selective and sensitive liquid chromatography coupled with atmospheric pressure chemical ionization tandem mass spectrometry (LC‐APCI‐MS‐MS) was developed and validated for the quantitation and pharmacokinetic study of carbazochrome sodium sulfonate in human plasma. Protein precipitation with 14% perchloric acid solution was selected for sample preparation, and amiloride hydrochloride was employed as an internal standard. The analytes were separated on a Hypersil ODS‐2 column by a multiple‐step linear gradient elution with a mobile phase consisting of 0.2% formic acid solution and methanol pumped at a flow rate of 1.0 mL/min. The determination was optimized and carried out with positive atmospheric pressure chemical ionization by selective reaction monitoring of the ion of m/z 148, the protonated thermodegraded fragment of the free acidic form of carbazochrome sodium sulfonate selected as the parent, and the ion of m/z 107 as the optimum collision induced dissociation (CID) product. The method was fully validated over a concentration range of 0.5–50 ng/mL, with the lower limit of quantitation of 0.5 ng/mL. The application of the LC‐MS‐MS method was demonstrated for the specific and quantitative analysis of carbazochrome sodium sulfonate in human plasma from a pharmacokinetic study in 24 healthy male Chinese volunteers after a single oral administration of 90 mg carbazochrome sodium sulfonate capsules. Copyright © 2010 John Wiley & Sons, Ltd.     

Simultaneous determination of neochlorogenic acid,chlorogenic acid,cryptochlorogenic acid and geniposide in rat plasma by UPLC‐MS/MS and its application to a pharmacokinetic study after administration of Reduning injection

A simple, specific and sensitive ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method was established and validated for simultaneous determination of neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid and geniposide in rat plasma using puerarin as an internal standard (IS). Plasma samples were pretreated by a one‐step direct protein precipitation procedure with acetonitrile after acidified using as little as 50 μL plasma. Chromatographic separation was performed on an Acquity BEH C₁₈ column (100 × 2.1 mm, 1.7 µm) at a flow rate of 0.2 mL/min by a gradient elution, using 0.2% acetic acid–methanol as mobile phase. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring via electrospray ionization source with negative ion mode. Calibration curves showed good linearity (r > 0.995) over wide concentration ranges. The intra‐ and inter‐day precisions were <15%, and the accuracy was within ±8.0%. The validated method was successfully applied to a pharmacokinetic study of the four bioactive components in rats after intravenous administration of Reduning injection. Copyright © 2014 John Wiley & Sons, Ltd.     

An LC‐MS/MS method for determination of 3,6′‐disinapoylsucrose in rat plasma and its application to a pharmacokinetic study

3,6′‐Disinapoylsucrose (DSS), a major active component of traditional Chinese medicine Yuan‐Zhi (the roots of Polygala tenuifolia), has significant effects for neuroprotection and improving learning memory. In order to explore the pharmacokinetic properties of DSS so as to further understand its in vivo activities, a sensitive LC‐MS/MS method was developed for determination of DSS in rat plasma and applied to a pharmacokinetic study in the present study. After treatment by protein precipitation, the plasma sample was separated on a C₁₈ HPLC column and analyzed by a mass spectrometry under positive electrospray ionization. Multiple‐reaction monitoring was employed to measure the ion transition at m/z 777.4 → 409.2 for DSS and m/z 557.2 → 309.1 for forsythin as internal standard. The method was linear over the studied concentration range of 0.5–1000.0 ng/mL. The precision and accuracy ranged from 1.4 to 18.4%, and from ?3.7 to ?9.5%, respectively, for within‐day and between‐day assay. Extraction recovery was higher than 86.6%. The limits of detection and quantification were 0.3 and 0.5 ng/mL, respectively. The present method was successfully applied to a pharmacokinetic study. DSS was found to have poor oral absorption with only about 0.5% bioavailability. Copyright © 2009 John Wiley & Sons, Ltd.     

Simultaneous determination of three active components in rat plasma by UPLC–MS/MS: Application to pharmacokinetic study after oral administration of Herba Sarcandrae extract

A rapid, specific and sensitive ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method was developed and validated for determination of isofraxidin, rosmarinic acid and kaempferol‐3‐O ‐glucuronide in rat plasma using warfarin as an internal standard (IS). Separation was conducted on a Thermo Hypersil GOLD C₁₈ column with linear gradient elution using methanol and water. Mass spectrometric detection was conducted using selected reaction monitoring (SRM) via an electrospray ionization (ESI) source. All analytes exhibited good linearity within their concentration ranges (r > 0.9990). The lower limits of quantitations of isofraxidin, rosmarinic acid, and kaempferol‐3‐O‐ glucuronide were 1.31, 0.67 and 0.92 ng/mL, respectively. Intra‐ and inter‐day precisions of these investigated components exhibited an RSD within 11.7%, and the accuracy ranged from −12.5 to 15.0% at all QC levels. The developed method was successfully applied to a pharmacokinetic study of isofraxidin, rosmarinic acid, and kaempferol‐3‐O‐ glucuronide in rats after oral administration of Herba Sarcandrae Extract.     

Rapid simultaneous determination of codeine and morphine in plasma using LC‐ESI‐MS/MS: Application to a clinical pharmacokinetic study

A rapid and sensitive high‐performance LC‐MS/MS method was developed and validated for the simultaneous quantification of codeine and its metabolite morphine in human plasma using donepezil as an internal standard (IS). Following a single liquid‐liquid extraction with ethyl acetate, the analytes were separated using an isocratic mobile phase on a C₁₈ column and analyzed by MS/MS in the selected reaction monitoring mode using the respective [M+H]⁺ ions, mass‐to‐charge ratio (m/z) 300/165 for codeine, m/z 286/165 for morphine and m/z 380/91 for IS. The method exhibited a linear dynamic range of 0.2–100/0.5–250 ng/mL for codeine/morphine in human plasma, respectively. The lower LOQs were 0.2 and 0.5 ng/mL for codeine and its metabolite morphine using 0.5 mL of human plasma. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated LC‐MS/MS method was applied to a pharmacokinetic study in which healthy Chinese volunteers each received a single oral dose of 30 mg codeine phosphate.     

Ultra‐performance liquid chromatography–tandem mass spectrometric assay for the simultaneous determination of brucine,strychnine and brucine N‐oxide in rat plasma: application to a pharmacokinetic study

A rapid, simple and sensitive UHPLC‐MS/MS method was developed and validated for the simultaneous determination of brucine, strychnine and brucine N‐oxide in rat plasma using huperzine A as an internal standard (IS) after protein precipitation with methanol. The analytes were separated on a Purospher® STAR RP₁₈ UHPLC column (2 µm, 2.1 × 100 mm) by gradient elution using a mobile phase composed of methanol and water (containing 0.1% formic acid) at a flow rate of 0.3 mL/min. Brucine, strychnine, brucine N‐oxide and IS were detected in positive ion multiple reaction monitoring mode by means of an electrospray ionization interface (m/z 395.2 → 324.1, m/z 335.2 → 184.1, m/z 411.2 → 394.2, m/z 243.1 → 226.1). The calibration curve was linear over the range of 1–500 ng/mL for brucine and strychnine and 0.2?50 ng/mL for brucine N‐oxide. The intra‐ and inter‐day precisions of these analytes were all within 15% and the accuracy ranged from 85 to 115%. The stability experiment indicated that the plasma samples at three concentration levels were stable under different conditions. The developed method was successfully applied for the first time to pharmacokinetic studies of brucine, strychnine and brucine N‐oxide following a single oral and intravenous administration of modified total alkaloid fraction in rats. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

An LC–MS/MS method for simultaneous determination of 1,5‐dicaffeoylquinic acid and 1‐O‐acetylbritannilactone in rat plasma and its application to a pharmacokinetic study

A selective and sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for the simultaneous quantitative determination of 1,5‐dicaffeoylquinic acid (1,5‐DCQA) and 1‐O‐ acetylbritannilactone (1‐O‐ ABL) in rat plasma. Chromatographic separation was performed on a Zorbax Eclipse XDB‐C₁₈ column using isocratic mobile phase consisting of methanol–water–formic acid (70:30:0.1, v /v/v) at a flow rate of 0.25 mL/min. The detection was achieved using a triple‐quadrupole tandem MS in selected reaction monitoring mode. The calibration curves of all analytes in plasma showed good linearity over the concentration ranges of 0.850–213 ng/mL for 1,5‐DCQA, and 0.520–130 ng/mL for 1‐O‐ ABL, respectively. The extraction recoveries were ≥78.5%, and the matrix effect ranged from 91.4 to 102.7% in all the plasma samples. The method was successfully applied for the pharmacokinetic study of the two active components in the collected plasma following oral administration of Inula britannica extract in rats.     

Sensitive LC‐MS‐MS method for the determination of tiopronin in human plasma

A highly selective and sensitive LC‐MS‐MS method was developed and validated to quantify tiopronin in human plasma, using fudosteine as the internal standard (IS). L ‐Cysteine and 1,4‐dithiothreitol (DTT) were used as the reducer and the stabilizer to release and stabilify tiopronin from a dimmer and mix forms with endogenous thiols in the treatment of plasma samples. After a simple liquid–liquid extraction with ethyl acetate in acidic condition, the post‐treatment samples were analyzed on a C₁₈ column interfaced with a triple‐quadruple tandem mass spectrometer using negative electrospray ionization. Methanol and water (40:60, v/v) were used as the isocratic mobile phase, with 0.2% formic acid and 1.0 mM tris (hydroxymethyl) aminomethane (Tris) in water. The method was validated to demonstrate the specificity, lower limit of quantification, accuracy and precision of measurements. The assay was linear over the concentration range 0.078–10 μg/mL. The correlation coefficients for the calibration curves ranged from 0.9980 to 0.9990. The intra‐ and inter‐day precisions, calculated from quality control samples, were not more than 10.49%. The method was employed in a pharmacokinetic study after oral administration of 200 mg tiopronin tablets to 24 healthy volunteers. Copyright © 2009 John Wiley & Sons, Ltd     

A fast,sensitive, and high‐throughput method for the simultaneous quantitation of three ellagitannins from Euphorbiae pekinensis Radix in rat plasma by ultra‐HPLC–MS/MS

A fast, sensitive, and high‐throughput ultra‐HPLC–MS/MS method has been developed and validated for the simultaneous determination of three main active constituents of Euphorbiae pekinensis Radix in rat plasma. After addition of the internal standard, plasma samples were extracted by liquid–liquid extraction with ethyl acetate/isopropanol (1:1, v/v) and separated on a CAPCELL PAK C₁₈ column (100 × 2.0 mm, 2 μm, Shiseido, Japan), using a gradient mobile phase system of methanol/water. The detection of the analytes was performed on a 4000Q UHPLC–MS/MS system with turbo ion spray source in the negative ion and multiple reaction‐monitoring mode. The linear range was 1.0–1000 ng/mL for 3,3′‐di‐O‐methyl ellagic acid‐4′‐O‐β‐d ‐glucopyranoside (i), 1.5–1500 ng/mL for 3,3′‐di‐O‐methyl ellagic acid‐4′‐O‐β‐d ‐xylopyranoside (ii), and 5.0–5000 ng/mL for 3,3′‐di‐O‐methyl ellagic acid (iii). The intra‐ and interday precision and accuracy of all the analytes were within 15%. The extraction recoveries of the three analytes and internal standard from plasma were all more than 80%. The validated method was first successfully applied to the evaluation of pharmacokinetic parameters of compounds 1 , 2 , and 3 in rat plasma after intragastric administration of the Euphorbiae pekinensis Radix extract.     

A chiral LC‐MS/MS method for the enantioselective determination of R‐(+)‐ and S‐(–)‐pantoprazole in human plasma and its application to a pharmacokinetic study of S‐(–)‐pantoprazole sodium injection

Pantoprazole, a proton pump inhibitor, is clinically used for the treatment of peptic diseases. An enantioselective LC‐MS/MS method was developed and validated for the simultaneous determination of pantoprazole enantiomers in human plasma. Pantoprazole enantiomers and the internal standard were extracted from plasma using acetonitrile. Chiral separation was carried on a Chiralpak IE column using the mobile phase consisted of 10 mm ammonium acetate solution containing 0.1% acetic acid–acetonitrile (28 : 72, v /v). MS analysis was performed on an API 4000 mass spectrometer. Multiple reactions monitoring transitions of m /z 384.1→200.1 and 390.1→206.0 were used to quantify pantoprazole enantiomers and internal standard, respectively. For each enantiomer, no apparent matrix effect was found, the calibration curve was linear over 5.00–10,000 ng/mL, the intra‐ and inter‐day precisions were below 10.0%, and the accuracy was within the range of –5.6% to 0.6%. This method was applied to the stereoselective pharmacokinetic studies in human after intravenous administration of S ‐(–)‐pantoprazole sodium injections. No chiral inversion was observed during sample storage, preparation procedure and analysis. While R ‐(+)‐pantoprazole was detected in human plasma with a slightly high concentration, which implied that S ‐(–)‐pantoprazole may convert to R ‐(+)‐pantoprazole in some subjects.     

LC‐MS/MS methods for the determination of edaravone and/or taurine in rat plasma and its application to a pharmacokinetic study

Three liquid chromatography–tandem mass spectrometry (LC‐MS/MS) methods were respectively developed and validated for the simultaneous or independent determination of taurine and edaravone in rat plasma using 3‐methyl‐1‐p‐tolyl‐5‐pyrazolone and sulfanilic acid as the internal standards (IS). Chromatographic separations were achieved on an Agilent Zorbax SB‐Aq (100 × 2.1 mm, 3.5 µm) column. Gradient 0.03% formic acid–methanol, isocratic 0.1% formic acid–methanol (90:10) and 0.02% formic acid–methanol (40:60) were respectively selected as the mobile phase for the simultaneous determination of two analytes, taurine or edaravone alone. The MS acquisition was performed in multiple reaction monitoring mode with a positive and negative electrospray ionization source. The mass transitions monitored were m/z [M + H]⁺ 175.1 → 133.0 and [M + H]⁺ 189.2 → 147.0 for edaravone and its IS, m/z [M ? H]^? 124.1 → 80.0 and [M ? H]^? 172.0 → 80.0 for taurine and its IS, respectively. The validated methods were successfully applied to study the pharmacokinetic interaction of taurine and edaravone in rats after independent intravenous administration and co‐administration with a single dose. Our collective results showed that there were no significant alterations on the main pharmacokinetic parameters (area under concentration–time curve, mean residence time, half‐life and clearance) of taurine and edaravone, implying that the proposed combination therapy was pharmacologically feasible. Copyright © 2014 John Wiley & Sons, Ltd.     

LC‐MS/MS method for the determination of agomelatine in human plasma and its application to a pharmacokinetic study

A sensitive and selective LC‐MS/MS method for the determination of agomelatine in human plasma was developed and validated. After simple liquid–liquid extraction, the analytes were separated on a Zorbax SB‐C₁₈ column (150 × 2.1 mm i.d., 5 µm) with an isocratic mobile phase consisting of 5 mm ammonium acetate solution (containing 0.1% formic acid) and methanol (30:70, v/v) at a flow‐rate of 0.3 mL/min. The MS acquisition was performed in multiple reaction monitoring mode with a positive electrospray ionization source. The mass transitions monitored were m/z 244.1 → 185.3 and m/z 285.2 → 193.2 for agomelatine and internal standard, respectively. The methods were validated for selectivity, carry‐over, matrix effects, calibration curves, accuracy and precision, extraction recoveries, dilution integrity and stability. The validated method was successfully applied to a pharmacokinetic study of agomelatine in Chinese volunteers following a single oral dose of 25 mg agomelatine tablet. Copyright © 2013 John Wiley & Sons, Ltd.     

Identification and determination of the major constituents in Kai‐Xin‐San by UPLC‐Q/TOF MS and UFLC‐MS/MS method

In order to have overall chemical material information of Kai‐Xin‐San (KXS), the reliable ultra‐high‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometer (UHPLC–Q‐TOF‐MS) and ultra‐fast liquid chromatography mass spectrometer (UFLC‐MS/MS) methods were developed for the identification and determination of the major constituents in KXS. Moreover, the UHPLC–Q‐TOF‐MS method was also applied to screen for multiple absorbed components in rat plasma after oral administration of KXS. The UHPLC–Q‐TOF‐MS method was achieved on Agilent 6520 Q‐TOF mass and operated in the negative ion mode. Good separation was performed on a ZORBAX Eclipse Plus C18 column with a gradient elution at a flow rate of 0.2 ml/min. A total of 92 compounds in KXS were identified or tentatively characterized based on their exact molecular weights, fragmentation patterns, and literature data. A total of 26 compounds including 23 prototype components and three metabolites were identified in rat plasma after oral administration of KXS. Then, 16 major bioactive constituents were chosen as the benchmark substances to evaluate the quality of KXS. Their quantitative analyses were performed by a triple quadrupole tandem mass spectrometer (MS/MS) operating in multiple‐reaction monitoring mode(MRM). The analysis was completed with a gradient elution at a flow rate of 0.4 ml/min within 35 min. The simple and fast method was validated and showed good linearity, precision, and recovery. Furthermore, the method was successful applied for the determination of 16 compounds in KXS. All results would provide essential data for identification and quality control of active chemical constituents in KXS. Copyright © 2016 John Wiley & Sons, Ltd.