Validated UHPLC–MS/MS assay for quantitative determination of etoposide,gemcitabine, vinorelbine and their metabolites in patients with lung cancer

A fully valid UHPLC–MS/MS method was developed for the determination of etoposide, gemcitabine, vinorelbine and their metabolites (etoposide catechol, 2′,2′‐difluorodeoxyuridine and 4‐O ‐deacetylvinorelbine) in human plasma. The multiple reaction monitoring mode was performed with an electrospray ionization interface operating in both the positive and negative ion modes per compound. The method required only 100 μL plasma with a one‐step simple de‐proteinization procedure, and a short run time of 7.5 min per sample. A Waters ACQUITY UPLC HSS T3 column (2.1 × 100 mm, 1.8 μm) provided chromatographic separation of analytes using a binary mobile phase gradient (A, 0.1% formic acid in acetonitrile, v /v; B, 0.1% formic acid in water, v /v). Linear coefficients of correlation were >0.995 for all analytes. The relative deviation of this method was <10% for intra‐ and inter‐day assays and the accuracy ranged between 86.35% and 113.44%. The mean extraction recovery and matrix effect of all the analytes were 62.07–105.46% and 93.67–105.87%, respectively. This method was successfully applied to clinical samples from patients with lung cancer.     

Fast simultaneous LC/MS/MS determination of 10 active compounds in human serum for therapeutic drug monitoring in psychiatric medication

A UPLC/MS/MS method with simple protein precipitation has been validated for the fast simultaneous analysis of agomelatine, asenapine, amisulpride, iloperidone, zotepine, melperone, ziprasidone, vilazodone, aripiprazole and its metabolite dehydro‐aripiprazole in human serum. Alprenolol was applied as an internal standard. A BEH C₁₈ (2.1 × 50 mm, 1.7 µm) column provided chromatographic separation of analytes using a binary mobile phase gradient (A, 2 mmol/L ammonium acetate, 0.1% formic acid in 5% acetonitrile, v/v/v; B, 2 mmol/L ammonium acetate, 0.1% formic acid in 95% acetonitrile, v/v/v). Mass spectrometric detection was performed in the positive electrospray ionization mode and ion suppression owing to matrix effects was evaluated. The validation criteria were determined: linearity, precision, accuracy, recovery, limit of detection, limit of quantification, reproducibility and matrix effect. The concentration range was as follows: 0.25–1000 ng/mL for agomelatine; 0.25–100 ng/mL for asenapine and iloperidone; 2.5–1000 ng/mL for amisulpride, aripiprazole, vilazodone and zotepine; 2.3–924.6 ng/mL for dehydroaripiprazole; 2.2–878.4 ng/mL for melperone; and 2.2–883.5 ng/mL for ziprasidone. Limits of quantitation below a therapeutic reference range were achieved for all analytes. Intra‐run precision of 0.4–5.5 %, inter‐run precision of 0.6–8.2% and overall recovery of 87.9–114.1% were obtained. The validated method was successfully implemented into routine practice for therapeutic drug monitoring in our hospital. Copyright © 2015 John Wiley & Sons, Ltd.     

Liquid chromatography mass spectrometry for the determination of salvianolic acid B,a natural compound from the herb Danshen in rat plasma and application to pharmacokinetic study

A sensitive and specific liquid chromatographic–electrospray ionization mass spectrometric method was developed for quantification of salvianolic acid B in rat plasma with resveratrol as the internal standard. The analytes were separated on a reversed‐phase column with acetonitrile (40%) and water (60%) containing 0.75% formic acid as mobile phase at a flow rate of 1 mL/min. Liquid–liquid extraction was adopted for the sample preparation, and the analytes were determined using electrospray negative ionization mass spectrometry in the selective monitoring mode. The method was validated over the concentration range 0.1–40 µg/mL using 0.1 mL of plasma with coefficients of correlation >0.999. The intra‐ and inter‐day precisions of analysis were <10%, and accuracy ranged from 94 to 101%. This method was successfully applied to a pharmacokinetics of salvianolic acid B in rats. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of a fast LC‐MS/MS assay for the determination of deferiprone in human plasma and application to pharmacokinetics

A fast and accurate liquid chromatography/tandem mass spectrometric (LC‐MS/MS) assay was first developed and validated for the determination of deferiprone in human plasma. The analytes were extracted with acetonitrile from only 50 μL aliquots of human plasma to achieve the protein precipitation. After extraction, chromatographic separation of analytes in human plasma was performed using a Synergi Fusion‐RP 80A column at 30 °C. The mobile phase consisted of methanol and 0.2% formic acid containing 0.2 mM EDTA (60:40, v/v). The flow rate of the mobile phase was 0.8 mL/min. The total run time for each sample analysis was 4 min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring mode by monitoring the precursor‐to‐parent ion transitions m/z 140.1 → 53.1 for deferiprone and m/z 143.1 → 98.1 for internal standard. A linear range was established from 0.1 to 20 µg/mL. The limit of detection was determined as 0.05 µg/mL. The validated method was estimated for linearity, recovery, stability, precision and accuracy. Intraday and interday precisions were 4.3–5.5 and 4.6–7.3%, respectively. The recovery of deferiprone was in the range of 80.1–86.8%. The method was successfully applied to a pharmacokinetic study of deferiprone in six thalassemia patients. Copyright © 2012 John Wiley & Sons, Ltd.     

Development of an LC‐MS/MS method for quantification of kadsurenone in rat plasma and its application to a pharmacokinetic study

A sensitive and rapid LC‐MS/MS method was developed and validated for the determination of kadsurenone in rat plasma using lysionotin as the internal standard (IS). The analytes were extracted from rat plasma with acetonitrile and separated on a SB‐C₁₈ column (50 × 2.1 mm, i.d.; 1.8 µm) at 30 °C. Elution was achieved with a mobile phase consisting of methanol–water–formic acid (65:35:0.1, v/v/v) at a flow rate of 0.30 mL/min. Detection and quantification for analytes were performed by mass spectrometry in the multiple reaction monitoring mode with positive electrospray ionization m/z at 357.1 → 178.1 for kadsurenone, and m/z 345.1 → 315.1 for IS. Calibration curves were linear over a concentration range of 4.88–1464 ng/mL with a lower limit of quantification of 4.88 ng/mL. The intra‐ and inter‐day accuracies and precisions were <8.9%. The LC‐MS/MS assay was successfully applied for oral pharmacokinetic evaluation of kadsurenone using the rat as an animal model. Copyright © 2013 John Wiley & Sons, Ltd.     

Development of a rapid and sensitive SPE-LC-MS/MS method for the simultaneous estimation of fluoxetine and olanzapine in human plasma

A high‐performance liquid chromatographic assay with tandem mass spectrometric detection was developed to simultaneously quantify fluoxetine and olanzapine in human plasma. The analytes and the internal standard (IS) duloxetine were extracted from 500 μL aliquots of human plasma through solid‐phase extraction. Chromatographic separation was achieved in a run time of 4.0 min on a Hypersil Gold C₁₈ column (50 × 4.6 mm, 5 µm) using isocratic mobile phase consisting of acetonitrile–water containing 2% formic acid (70:30, v/v), at a flow‐rate of 0.5 mL/min. Detection of analytes and internal standard was performed by electrospray ionization tandem mass spectrometry, operating in positive‐ion and multiple reaction monitoring acquisition mode. The protonated precursor to product ion transitions monitored for fluoxetine, olanzapine and IS were m/z 310.01 → 147.69, 313.15 → 256.14 and 298.1 → 153.97, respectively. The method was validated over the concentration range of 1.00–150.20 ng/mL for fluoxetine and 0.12–25.03 ng/mL for olanzapine in human plasma. The intra‐batch and inter‐batch precision (%CV) across four quality control levels was ≤6.28% for both the analytes. In conclusion, a simple and sensitive analytical method was developed and validated in human plasma. This method is suitable for measuring accurate plasma concentration in bioequivalence study and therapeutic drug monitoring as well, following combined administration. Copyright © 2011 John Wiley & Sons, Ltd.     

Simultaneous quantification of two steroidal glycosides after oral gavage of Marsdenia tenacissima extract in rats using a LC‐MS/MS method

A specific, sensitive and accurate analytical LC‐MS/MS assay was developed for the simultaneous determination of two steroidal glycosides, tenacissoside H and tenacissoside I, in rat plasma. An Agilent ZORBAX SB‐C₁₈ column was used with an isocratic mobile phase system composed of methanol–water–formic acid (70:30:0.1, v/v/v) at a flow rate of 0.3 mL/min. The analysis was performed on a positive ionization electrospray mass spectrometer via selected reaction monitoring mode scan. One‐step protein precipitation with acetonitrile was chosen to extract the analytes from plasma. The lower limits of quantification were 0.9 ng/mL for tenacissoside H and tenacissoside I. The intra‐ and inter‐day precisions were 2.03–11.56 and 3.76–11.62%, respectively, and the accuracies were <110.28% at all quality control levels. The validated method was applied to a pharmacokinetic study in rats after oral gavage of Marsdenia tenacissima extract. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of wogonin,oroxylin a,schisandrin, paeoniflorin and emodin in rat serum by HPLC–MS/MS and application to pharmacokinetic studies

Wogonin and oroxylin A in Scutellariae Radix, schisandrin in Chinensis Fructus, paeoniflorin in Moutan Cortex and emodin in Polygoni Cuspidate Rhizome et Radix are anti‐inflammatory active compounds. A method for simultaneous determination of the five compounds in rat was developed and validated using high‐performance liquid chromatography with tandem mass spectrometry (HPLC–MS/MS). The separation was performed on a Symmetry C₁₈ column (4.6 × 50 mm, 3.5 μm) with acetonitrile and 0.1% formic acid aqueous solution as the mobile phases. The detection was performed using multiple‐reaction monitoring with electrospray ionization source in positive–negative ion mode. The calibration curves showed good linearity (r ≥ 0.9955). The lower limit of quantification (LLOQ) was 5 ng/mL for wogonin and schisandrin, 10 ng/mL for oroxylin A and emodin, and 15 ng/mL for paeoniflorin, respectively. The relative standard deviations of intraday and interday precisions were <11.49 and 14.28%, respectively. The extraction recoveries and matrix effects were acceptable. The analytes were stable under the experiment conditions. The validated method has been successfully applied to pharmacokinetic studies of the five compounds in rats after oral administration of Hu‐gan‐kan‐kang‐yuan capsule. This paper would be a valuable reference for pharmacokinetic studies of Chinese medicine preparations containing the five compounds.     

Studies on excretion kinetics of ten constituents in rat urine after oral administration of Shensong Yangxin Capsule by UPLC‐MS/MS

A rapid and sensitive ultra‐high performance liquid chromatography–mass spectrometry (UPLC‐MS/MS) method was developed and validated for the quantification of 10 major active constituents in rat urine after oral administration of Shensong Yangxin Capsule (SSYX) using diazepam as an internal standard (IS). The urine samples were pretreated and extracted by solid‐phase extraction prior to UPLC. Chromatographic separation was achieved on a Waters C₁₈ (2.1 × 50 mm, 1.7 µm) column using a gradient elution program with 0.1% formic acid aqueous solution and acetonitrile at a flow rate of 0.4 mL/min. Detection and quantitation were accomplished by a hybrid quadrupole mass spectrometer using electrospray ionization source and multiple reaction monitoring in the positive ionization mode. The mass transition ion‐pairs (m/z) for quantitation were all optimized and the total run time was 4.50 min. The specificity, linearity, accuracy, precision, recovery, matrix effect and stabilities were all validated for the analytes in urine samples. The validation results indicated that this method was simple, rapid, specific and reliable. The proposed method was successfully applied to investigate the urinary excretion kinetics of 10 compounds in rat after oral administration of SSYX. Copyright © 2013 John Wiley & Sons, Ltd.     

LC–MS/MS method for simultaneous determination of flavonoids and physalins in rat plasma: Application to pharmacokinetic study after oral administration of Physalis alkekengi var. franchetii (Chinese lantern) extract

A rapid and sensitive liquid chromatography with tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the simultaneous determination of luteolin, luteolin‐7‐O ‐β ‐D‐glucopyranoside, physalin A, physalin D and physalin L in rat plasma. Scutellarein and dexamethasone were used as the internal standards (IS). Plasma samples were prepared by liquid‐liquid extraction with ethyl acetate. The five constituents were separated on an Acquity UPLC BEH C₁₈ column (100 mm × 2.1 mm, 1.7 μm). A gradient elution procedure was used with acetonitrile (A)‐0.1% aqueous formic acid (B). Mass spectrometric detection was performed in negative ion multiple reaction monitoring mode with an electrospray ionization (ESI) source. This method showed good linearity (r ² > 0.997) over a concentration range of 2.0–500 ng/mL with a lower limit of quantification of 2.0 ng/mL for all five compounds. The inter‐ and intra‐day accuracy ranged from 91.7 to 104%, and precisions (RSD) were <6.46% for all analytes. The extraction recoveries of all analytes were >85%. This validated method was successfully applied for the first time to the pharmacokinetic study of five ingredients after oral administration of 70% ethanol extract of Chinese lantern in rats.     

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.     

An LC–MS/MS method for quantification of HR011303, a novel highly selective urate transporter 1 inhibitor in beagle dogs and the application to a pharmacokinetic study

HR011303 is a novel and highly selective urate transporter 1 (URAT1) inhibitor. In this study, a sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for quantification of HR011303 in beagle dog plasma. Plasma samples were pretreated with protein‐precipitation extraction by acetonitrile and added with a trifluoromethyl substituted analog of HR011303 as internal standard. The chromatographic separation was performed on a Shiseido C₁₈ column (100 × 4.6 mm, i.d., 5 μm) by mobile phases consisting of 5 mm ammonium–formic acid (100:0.1) and acetonitrile–formic acid (100:0.1) solutions in gradient elution. The MS detection was conducted in electrospray positive ionization with multiple reactions monitoring at m/z 338 → 240 for HR011303 and m/z 328 → 230 for the internal standard using 25 eV argon gas collision induced dissociation. The established LC–MS/MS method showed good selectivity, sensitivity, precision and accuracy. The plasma pharmacokinetics of HR011303 in beagle dogs following both oral and intravenous administration were then successfully evaluated using this LC–MS/MS method.     

A new HPLC–MS/MS method for the simultaneous quantification of SGLT2 inhibitors and metformin in plasma and its application to a pharmacokinetic study in healthy volunteers

Monitoring the plasma concentrations of metformin and sodium‐glucose cotransporter‐2 inhibitors (canagliflozin, dapagliflozin and empagliflozin) is essential for pharmacokinetic and bioequivalence studies and therapeutic monitoring. The present work therefore aimed to develop and validate a high‐performance liquid chromatography coupled to tandem mass spectrometry (HPLC–MS/MS) method for the simultaneous quantification of these drugs in human plasma. The analyses were performed using an Agilent 1200 HPLC system coupled to an Applied Biosystems API 3200 triple quadrupole MS/MS with electrospray ionization in positive ion mode. After one‐step protein precipitation of plasma with acetonitrile containing 0.1% formic acid, chromatographic separation was achieved on an Xbridge C₁₈ column, with a mobile phase consisting of a gradient of water and acetonitrile, both containing 1 mm ammonium formate and 0.1% formic acid. Quantification was performed in multiple reaction monitoring mode using m/z 130.1 → 71.1 for metformin, m/z 462.0 → 191.2 for canagliflozin, m/z 426.1 → 167.1 for dapagliflozin and m/z 468.0 → 354.9 for empagliflozin. The proposed method was validated and demonstrated to be adequate for the quantification of metformin, canagliflozin, dapagliflozin and empagliflozin for clinical monitoring, pharmacokinetics and bioequivalence studies.     

Simultaneous determination of ginsenosides and bufadienolides in rat plasma after the oral administration of Shexiang Baoxin Pill for pharmacokinetic study by liquid chromatography tandem mass spectrometry following solid‐phase extraction

A sensitive and reliable bioanalytical method was established for quantitati\ve and pharmacokinetic investigation of nine ginsenosides and seven bufadienolides in rat plasma after the oral administration of Shexiang Baoxin Pill by liquid chromatography–electrospray ionization tandem mass spectrometry, using tinidazole and digoxin as internal standards (ISTDs). All of the analytes and ISTDs obtained satisfactory recoveries by solid‐phase extraction using an Oasis HLB μElution Plate, which was eluted with methanol and ethyl acetate successively, and chromatographic separation was achieved on a Shim‐pack XR‐ODSIIcolumn (75 × 2.0 mm, 2.2 μm) with gradient elution using a mixture of acetonitrile–0.1% formic acid solution (v /v) as the mobile phase at a flow rate of 0.3 mL/min. Detection was carried out by a triple‐quadrupole tandem mass spectrometry with positive/negative ion switching multiple reaction monitoring mode. All analytes showed good linearity over a wide concentration range (r ² > 0.99). The lower limit of quantification was in the range 0.625–12.5 ng/mL for bufadienolides and 2–5.5 ng/mL for ginsenosides, and the mean recoveries of all analytes were in the range 78.29–99.35%. The intra‐ and inter‐day precisions (RSD) were in the range 0.08–12.38% with the accuracies between 86.09 and 99.40%. The validated method was then successfully applied to pharmacokinetic study of the above 16 compounds in rat plasma. Pharmacokinetic results indicated that the developed extraction and analytical method could be employed as a rapid, effective technique for pharmacokinetic study of multiple components, especially various polarity that are difficult to extract simultaneously.     

Simultaneous determination of evobrutinib and its metabolite evobrutinib‐diol in dog plasma by liquid chromatography combined with electrospray ionization tandem mass spectrometry

A rapid and sensitive liquid chromatography hyphenated with electrospray ionization tandem mass spectrometric method (LC–ESI–MS/MS) was developed and validated for simultaneous determination of evobrutinib and evobrutinib‐diol in dog plasma. The plasma sample was processed using acetonitrile and chromatographic separation was carried out on a Waters Acquity BEH C₁₈ column (50 × 2.1 mm, 1.7 μm). The mobile phase was composed of 0.1% formic acid and acetonitrile, with an optimized gradient elution at a flow rate of 0.4 mL/min. Detection was accomplished in selective reaction monitoring mode via electrospray ionization interface operated in positive ion mode. The precursor‐to‐product transitions for quantification were m/z 430.2 → 98.1 for evobrutinib, m/z 464.2 → 98.1 for evobrutinib‐diol and m/z 441.2 → 138.1 for ibrutinib (internal standard). The developed assay was linear over the tested concentration ranges with correlation coefficient >0.995. The LLOQ was 0.1 ng/mL for both analytes. The inter‐ and intra‐day precisions were <9.65% and the accuracy ranged from ?3.94 to 6.37%. The extraction recovery was >85.41% and no significant matrix effect was observed. The developed assay was successfully applied to the pharmacokinetic study of evobrutinib and evobrutinib‐diol in dogs after oral administration of evobrutinib at a single dose of 5 mg/kg.     

Simultaneous determination of four secoiridoid and iridoid glycosides in rat plasma by ultra performance liquid chromatography–tandem mass spectrometry and its application to a comparative pharmacokinetic study

A simple, reliable and rapid ultra‐performance liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous quantification of four secoiridoid (gentiopicroside, swertiamarin, sweroside) and iridoid glycosides (loganic acid), the bio‐active ingredients in rat plasma. After liquid–liquid extraction, chromatographic separation was accomplished on a Shim‐pack XR‐ODS column with a mobile phase consisting of methanol and 0.1% formic acid in water. A triple quadrupole tandem mass spectrometry equipped with an electrospray ionization source was used as detector operating both in positive and negative ionization mode and operated by multiple‐reaction monitoring scanning. The lower limits of quantitation were 0.25–30 ng/mL for all the analytes. Both intra‐day and inter‐day precision and accuracy of analytes were well within acceptance criteria (±15%). The mean extraction recoveries of analytes and internal standard (amygdalin) from rat plasma were all >71.4%. The validated method was successfully applied to a comparative pharmacokinetic study of four analytes in rat plasma between normal and arthritic rats after oral administration of Huo Luo Xiao Ling Dan and Gentiana macrophylla extract, respectively. Results showed significant differences in pharmacokinetic properties of the analytes among the different groups. Copyright © 2015 John Wiley & Sons, Ltd.     

Pharmacokinetic comparison of five tanshinones in normal and arthritic rats after oral administration of Huo Luo Xiao Ling Dan or its single herb extract by UPLC‐MS/MS

A fast, sensitive and reliable ultra performance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) method has been developed and validated for simultaneous quantitation and pharmacokinetic study of five tanshinones (tanshinone I, tanshinone IIA, tanshinone IIB, dihydrotanshinone I, cryptotanshinone), the bio‐active ingredients of Huo Luo Xiao Ling Dan (HLXLD) in rat plasma. After liquid–liquid extraction, chromatographic separation was accomplished on a Shim‐pack XR‐ODS column (75 × 3.0 mm, 2.2 µm particles) and eluted with a mobile phase consisting of acetonitrile–0.05% formic acid aqueous solution (80:20, v/v) at a flow rate of 0.4 mL/min, and the total run time was 7.0 min. The detection was performed on a triple quadrupole tandem mass spectrometry equipped with an electrospray ionization source in positive ionization and multiple reaction monitoring mode. The lower limits of quantification were 0.050–0.400 ng/mL for all the analytes. Linearity, precision and accuracy, the mean extraction recoveries and matrix effects all satisfied criteria for acceptance. This validated method was successfully applied to a comparative pharmacokinetic study of five bio‐active components in rat plasma after oral administration of HLXLD or Salvia miltiorrhiza extract in normal and arthritic rats. The results showed that there were different pharmacokinetic characteristics among different groups. Copyright © 2016 John Wiley & Sons, Ltd.     

Simultaneous determination of atorvastatin and niacin in human plasma by LC-MS/MS and its application to a human pharmacokinetic study

A rapid, simple, sensitive and selective LC‐MS/MS method has been developed and validated for quantification of the atorvastatin (AT) and niacin (NA) in 250 μL human plasma. The analytical procedure involves a liquid–liquid extraction method using nevirapine as an internal standard (IS). The chromatographic separation was achieved on a Hypurity Advance (4.6 × 50 mm, 5 µm) column using a mobile phase consisting of 0.1% formic acid buffer–acetonitrile (20:80, v/v) at flow rate of 0.8 mL/min. The API‐4000 LC‐MS/MS was operated in the multiple‐reaction monitoring mode using electrospray ionization. The total run time of analysis was 3 min and elution of AT, NA and IS occurred at 1.06, 1.84 and 0.92 min, respectively. A detailed validation of the method was performed as per the US Food and Drug Administration guidelines and the standard curves found to be linear in the range of 0.10–30.0 ng/mL for AT and 20.2–6026 ng/mL for NA, with a coefficient of correlation of ≥0.99 for both the compounds. AT and NA were found to be stable in a battery of stability studies, viz. bench‐top, autosampler, re‐injection, wet‐extract and repeated freeze–thaw cycles. The developed assay method was successfully applied to a pharmacokinetic study in humans. Copyright © 2012 John Wiley & Sons, Ltd.     

LC–MS/MS method for the simultaneous determination of ethyl gallate and its major metabolite in rat plasma

A simple, rapid and sensitive liquid chromatography–tandem mass spectroscopy (LC–MS/MS) method was developed and validated for the determination of ethyl gallate, a pharmacologically active constituent isolated from Lagerstroemia speciosa (Linn.) Pers. This method was used to examine the pharmacokinetics of ethyl gallate and its major metabolite gallic acid in rat plasma using propyl gallate as an internal standard. After precipitation of the plasma proteins with acetonitrile, the analytes were separated on a Zorbax SB‐C₁₈ column (3.5 μm, 2.1 × 50 mm) with an isocratic mobile phase consisted of methanol–acetonitrile–10 mM ammonium acetate (10 : 25 : 65, v/v/v) containing 0.1% formic acid at a flow rate of 0.25 mL/min. The Agilent G6410A triple quadrupole LC/MS system was operated under the multiple‐reaction monitoring mode using the electrospray ionization technique in negative mode. The lower limits of quantification of gallic acid and ethyl gallate of the method were 0.5 and 1.0 ng/mL. The intra‐day and inter‐day accuracy and precision of the assay were less than 8.0%. This method has been applied successfully to a pharmacokinetic study involving the intragastric administration of ethyl gallate to rats. Copyright © 2009 John Wiley & Sons, Ltd.     

A novel LC-MS/MS method for simultaneous quantification of tenofovir and lamivudine in human plasma and its application to a pharmacokinetic study

A new, rapid, sensitive and specific LC‐MS/MS method has been developed and validated for the simultaneous quantification of tenofovir and lamivudine in human plasma using abacavir as an internal standard. An API‐4000 LC‐MS/MS with electrospray ionization was operated in multiple‐reaction monitoring mode for the analysis. The analytes were extracted from plasma by solid‐phase extraction technique using an Oasis HLB cartridge. The reconstituted samples were chromatographed on a Chromolith ROD speed C₁₈ column using a mixture of 0.1% formic acid in water and acetonitrile (90:10 v/v) at a flow‐rate of 1 mL/min. The method was validated as per the FDA guidelines. The calibration curves were found to be linear in the range of 5–600 ng/mL for tenofovir and 25– 4000 ng/mL for lamivudine. The intra‐ and inter‐day precision and accuracy results were well within the acceptable limits. A run time of 2.8 min consumed for each sample made it possible to analyze more samples per day. The proposed assay method was found to be applicable to a pharmacokinetic study in human male volunteers. Copyright © 2012 John Wiley & Sons, Ltd.