Liquid chromatography–tandem mass spectrometry method of loxoprofen in human plasma

A rapid, sensitive and selective liquid chromatography–electrospray ionization mass spectrometric method for the determination of loxoprofen in human plasma was developed. Loxoprofen and ketoprofen (internal standard) were extracted from 20 µL of human plasma sample using ethyl acetate at acidic pH and analyzed on an Atlantis dC₁₈ column with the mobile phase of methanol:water (75:25, v/v). The analytes were quantified in the selected reaction monitoring mode. The standard curve was linear over the concentration range of 0.1–20 µg/mL with a lower limit of quantification of 0.1 µg/mL. The coefficient of variation and relative error for intra‐ and inter‐assay at four quality control levels were 2.8–5.2 and 4.8–7.0%, respectively. The recoveries of loxoprofen and ketoprofen were 69.7 and 67.6%, respectively. The matrix effects for loxoprofen and ketoprofen were practically absent. This method was successfully applied to the pharmacokinetic study of loxoprofen in humans. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of quinapril and quinaprilat in human plasma by ultraperformance liquid chromatography–electrospray ionization mass spectrometry

A novel, specific and sensitive ultraperformance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method was developed for the simultaneous determination of quinapril and its active metabolite quinaprilat in human plasma. The method involves a simple, one‐step extraction procedure coupled with an Acquity UPLC? BEH C₁₈ column (100 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow‐rate of 0.2 mL/min and lisinopril as the internal standard. Detection was performed on a triple‐quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionization. Using 250 µL plasma, the methods were validated over the concentration range 5.010–500.374 ng/mL for quinapril and 10.012–1000 ng/mL for quinaprilat, with a lower limit of quantification of 5.010 ng/mL for quinapril and 10.012 ng/mL for quinaprilat. The intra‐ and inter‐day precision and accuracy were within 10.0%. The recovery was 85.8, 62.6 and 61.3% for quinapril, quinaprilat and lisinopril, respectively. Total run time was 3.0 min only. Copyright © 2008 John Wiley & Sons, Ltd.     

Rapid and efficient method for the quantification of lychnopholide in rat plasma by liquid chromatography–tandem mass spectrometry for pharmacokinetic application

Lychnopholide is a sesquiterpene lactone usually obtained from Lychnophora and Eremanthus species and has pharmacological activities that include anti‐inflammatory and anti‐tumor. Lychnopholide isolated from Eremanthus matogrossenssis was analyzed in this study. The aims of this study were to develop and validate an analytical methodology by LC‐MS/MS and to quantify lychnopholide in rat plasma. Chromatographic separation was achieved on a C₁₈ column using isocratic elution with the mobile phase consisting of methanol and water (containing 0.1% formic acid) at a flow rate of 0.4 mL/min. The detection was performed in multiple‐reaction monitoring mode using electrospray ionization in positive mode. The method validation was performed in accordance with regulatory guidelines and the results met the acceptance criteria. The linear range of detection was 10–200 ng/mL (r > 0.9961). The intra‐ and inter‐day assay variability were <6.2 and <11.7%, respectively. The extraction recovery was approximately 63% using liquid–liquid extraction with chloroform. Lychnopholide was detected in plasma up to 60 min after intravenous administration in rats. This rapid and sensitive method for the analysis of the sesquiterpene lactone lychnopholide in rat plasma can be applied to pharmacokinetic studies of this compound. Copyright © 2016 John Wiley & Sons, Ltd.     

Solid‐phase extraction and analysis of paroxetine in human plasma by ultra performance liquid chromatography–electrospray ionization mass spectrometry

A rapid, sensitive and rugged solid‐phase extraction ultra performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method was developed for determination of paroxetine in human plasma. The procedure for sample preparation includes simple SPE extraction procedure coupled with Hypersil Gold C₁₈ column (100 mm ? 2.1 mm, i.d., 1.9 μm) with isocratic elution at a flow‐rate of 0.350 mL/min and fluoxetine was used as the internal standard. The analysis was performed on a triple‐quadrupole tandem mass spectrometer by multiple reactions monitoring mode via electrospray ionization. Using 500 μL plasma, the methods were validated over the concentration range 0.050–16.710 ng/mL for paroxetine, with a lower limit of quantification of 0.050 ng/mL. The intra‐ and inter‐day precision and accuracy of the quality control samples were within 10.0%. The recovery was 69.2 and 74.4% for paroxetine and fluoxetine respectively. Total run time was only 1.9 min. The method was highly reproducible and gave peaks with excellent chromatography properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Quantitative determination of cefetamet in human plasma by liquid chromatography–mass spectrometry

Cefetamet is a potent antibiotic to treat respiratory and urinary tract infections. To improve oral bioavailability, it is administered as a prodrug, cefetamet pivoxyl hydrolyzed by esterase following absorption. A quantification method using a mass spectrometry was developed for the determination of cefetamet in human plasma. After a protein precipitation with acetonitrile, the analytes were chromatographed on a reversed‐phase C₁₈ column and detected by a tandem mass spectrometer with electrospray ionization. The accuracy and precision of the assay were in accordance with FDA regulations for the validation of bioanalytical methods. This method was used to measure the concentrations of the cefetamet in plasma after a single oral administration of 500 mg cefetamet pivoxyl. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of ecliptasaponin A in rat plasma and tissues by liquid chromatography‐tandem mass spectrometry

A sensitive, rapid and specific high‐performance liquid chromatography tandem mass spectrometry method (HPLC‐MS/MS) was developed to determine ecliptasaponin A in rat plasma and tissues after oral administration. Ginsenoside Rg1 was used as the internal standard (IS). The plasma and tissues samples were prepared by liquid‐liquid extraction with ethyl acetate and separated on an Eclipse Plus C₁₈ column (2.1 mm × 150 mm, 5 µm) at a flow rate of 0.4 mL/min using acetonitrile and water (containing 0.05% acetic acid) as the mobile phase. The tandem mass detection was carried out with eletrospray ionization in negative mode. Quantification was performed by using multiple reaction monitoring (MRM), which monitored the fragmentation of m/z 633.4→587.2 for ecliptasaponin A and m/z 859.4→637.4 for the IS. The calibration curves obtained were linear in different matrices, and the lower limit of quantification (LLOQ) achieved was 0.5 ng/mL both for rat plasma and tissues. The intra‐ and inter‐day precisions were below 15%. This method was successfully applied to pharmacokinetic study of ecliptasaponin A in rat plasma and tissues after oral administration. Copyright © 2015 John Wiley & Sons, Ltd.     

Liquid chromatography–tandem mass spectrometry method for simultaneous quantification of urapidil and aripiprazole in human plasma and its application to human pharmacokinetic study

A sensitive and selective liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of urapidil and aripiprazole in human plasma. A simple liquid–liquid extraction with ethyl acetate was used for the sample preparation. Chromatographic separation was achieved on a Phenomenex C₁₈ (4.6 × 50 mm, 5 µm) column with 0.1% formic acid–acetonitrile (10:90, v/v) as the mobile phase with flow rate of 0.6 mL/min. The quantitation of the target compounds was determined in a positive ion multiple reaction monitoring mode. Calibration plots were linear over the range of 2.0–2503.95 ng/mL for urapidil and 1.0–500.19 ng/mL for aripiprazole. The lower limit of quantitation for urapidil and aripiprazole was 2.0 and 1.0 ng/mL, respectively. Mean recovery was in the range of 69.94–75.62% for both analytes and internal standards. Intra‐day and inter‐day precisions of the assay at three concentrations were 2.56–5.89% with accuracy of 92.31–97.83% for urapidil, and 3.14–6.84% with accuracy of 91.38–94.42% for aripiprazole. The method was successfully applied to human pharmacokinetic study of urapidil and aripiprazole in healthy human male volunteers. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of drugs of abuse in bovine dentin using liquid chromatography–electrospray ionization tandem mass spectrometry

Drugs deposited in human teeth are well preserved; the spectrum of toxicological investigations may therefore be supplemented by an analysis method for drugs in teeth. A liquid chromatography–electrospray ionization tandem mass spectrometry assay for the detection and quantification of basic drugs of abuse in bovine dentin samples was developed and validated. The drugs and metabolites amphetamine, methamphetamine, methylenedioxymethylamphetamine, methylenedioxyethylamphetamine, codeine, morphine, cocaine and benzoylecgonine were extracted from 50 mg ground dentin powder by ultrasonication for 60 min in methanol 3 times. The extracts were analyzed on a triple‐quadrupole mass‐spectrometer in multiple reaction monitoring mode. The method was validated and proved to be accurate, precise, selective, specific and stable with good linearity within the calibration range and a lower limit of quantification of 10 to 20 pg/mg. To artificially load bovine dentin samples with drugs, the natural process of de‐ and remineralization in the oral cavity was mimicked by a pH‐cycling experiment. The artificially drug‐loaded dentin samples showed drug concentrations of 20 to 80 pg/mg. The method can be applied in further in vitro experiments as well as in post‐mortem cases, especially where limited sample tissue is available. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantification of an antitumor agent (copen) in rat plasma by liquid chromatography–electrospray ionization tandem mass spectrometry and its application in a preclinical pharmacokinetic study

Copen is a derivative obtained from the structural modification of osthole, which inhibits tumoral proliferation in many tumor cell lines. A rapid and sensitive liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was established for the quantification of copen in rat plasma. After a simple sample preparation procedure by one‐step protein precipitation with methanol, copen and bicalutamide (internal standard, IS) were chromatographed on a Zorbax SB‐C₁₈ (4.6×100 mm, 1.8 µm) column with a mobile phase consisting of methanol–5 mm ammonium formate water with 0.1% formic acid (80:20, v/v). MS detection was performed on a triple quadrupole tandem mass spectrometer in the multiple reaction monitoring mode with a positive eletrospray ionization source. The assay was validated in the concentration range of 51.58–20630 ng/mL, with a limit of quantitation (LOQ) of 51.58 ng/mL. The intra‐ and inter‐day precisions (relative standard deviation) were ≤3.21 and ≤11.3%, respectively, with accuracy (%) in the range of 94.66–102.1%. The method was fully validated in a study of the pharmacokinetics of copen (25 mg/kg) after intragastric administration in rats. Copyright © 2014 John Wiley & Sons, Ltd.     

Liquid chromatography–tandem mass spectrometric assay for the multikinase inhibitor regorafenib in plasma

Regorafenib has recently been approved for the treatment of colorectal cancer. A bioanalytical liquid chromatography–tandem mass spectrometric assay for this multikinase inhibitor was developed and validated in plasma. The concentration range of the assay was 25–25,000 ng/mL. Protein precipitation with acetonitrile was used as sample pre‐treatment with sorafenib as internal standard. The extract was diluted with methanol (25%, v/v) and then injected onto the sub‐2 µm particle, bridged ethylsilicia hybrid trifunctional bonded C₁₈ column. Isocratic elution using 0.02% (v/v) formic acid in a methanol–water mixture was used. Compounds were monitored by a triple quadrupole mass spectrometer in the selected reaction monitoring mode after positive electrospray ionization. Double logarithmic calibration was used; within‐day precisions, between‐day precisions, and accuracies were 3.2–9.2, 4.1–12.3 and 94.8–103.0%, respectively. High drug stability was observed under all relevant storage conditions. The assay was used to measure drug concentrations in a pharmacokinetic study in wild‐type FVB mice. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of corilagin in rat plasma using a liquid chromatography–electrospray ionization tandem mass spectrometric method

A sensitive and simple liquid chromatography–tandem mass spectrometric (HPLC‐MS/MS) method for the determination of corilagin in rat plasma has been developed. Samples were prepared with protein precipitation method and analyzed with a triple quadrupole tandem mass spectrometer. We employed negative electrospray ionization as the ionization source and the analytes were detected in multiple reaction monitoring mode. Separation was achieved on a C₈ column eluted with mobile phase consisting of methanol–0.1% formic acid in a gradient mode at the flow rate of 0.3 mL/min. The total run time was 7.0 min.This method was proved to have good linearity in the concentration range of 2.5–1000.0 ng/mL. The lower limit of quantification of corilagin was 2.5 ng/mL. The intra‐ and inter‐day relative standard deviationa across three validation runs for four concentration levels were both <9.8%. The relative error was within ±6.0%. This assay offers advantages in terms of expediency and suitability for the analysis of corilagin in rat plasma. The practical utility of this new HPLC‐MS/MS method was confirmed in pilot plasma concentration studies in rats following oral administration. Copyright © 2015 John Wiley & Sons, Ltd.     

Rapid ultraperformance liquid chromatography–tandem mass spectrometry method for quantification of oxcarbazepine and its metabolite in human plasma

A rapid and sensitive ultraperformance liquid chromatography tandem mass spectrometry assay was developed for the simultaneous analysis of oxcarbazepine and its main metabolite in human plasma. The assay involves a simple solid‐phase extraction procedure of 0.3 mL of human plasma and analysis was performed on a triple‐quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionization. Separation was achieved on an Acquity UPLC™ BEH C₁₈ column (50 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow‐rate of 0.25 mL/min and imipramine was used as the internal standard. The standard calibration curve was linear over the range 9.580–5070.205 ng/mL for oxcarbazepine (OXC) and 19.444–10290.800 ng/mL for 10,11‐dihydro‐10‐hydroxycarbamazepine (MHD), expressed by the linear correlation coefficient r², which was better than 0.995 for OXC and MHD. The intra‐ and inter‐day precision and accuracy of the quality control samples were within 10.0%. The recoveries were 81.0, 89.6 and 66.6% for OXC, MHD and imipramine, respectively. The total run time was 1.5 min only for each sample, which makes it possible to analyze more than 350 samples per day. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a liquid chromatography–isotope dilution mass spectrometry method for quantification of fentanyl in human plasma

Fentanyl is a potent analgesic drug in relieving chronic pain in patients. In this report, we present a simple, reliable and sensitive LC–ID/MS method for the quantification of fentanyl in human plasma. LC‐ID/MS analysis was carried out on a triple quadrupole mass spectrometer operated in positive electrospray ionization multiple‐reaction‐monitoring using the transitions m/z 337.6 → 187.9 for fentanyl and m/z 342.6 → 187.9 for the internal standard (D5‐fentanyl). The calibration curve covered the range 0.02–10 ng/mL. The intra‐ and inter‐batch precision were less than 6.739 and 3.126% for fentanyl and IS, with accuracy from 94.16 to 102.0%. The lower limit of quantification was identifiable and reproducible at 0.02 ng/mL. The validated method offered increased sensitivity and wide linear concentration range. This method was successfully adopted for the evaluation of bioequivalence of two fentanyl transdermal preparations after single dose administration to 20 Chinese pain‐patients. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of flomoxef in human plasma by liquid chromatography/electrospray ionization tandem mass spectrometry

A specific, sensitive, rapid and reproducible method for the determination of flomoxef in human plasma using high‐performance liquid chromatography–tandem mass spectrometry was developed and validated. Flomoxef was detected using an electrospay ionization method operated in negative‐ion mode. Chromatographic separation was performed in gradient elution mode on a Luna® C₁₈(2) column (3 μm , 20 × 4.0 mm) at a flow rate of 1 mL/min and runtime 3.5 min. The mobile phase consisted of acetonitrile and water containing 0.1% formic acid as additive. Extraction of flomoxef from plasma and precipitation of plasma proteins was performed with acetonitrile with an absolute recovery of 86.4 ± 1.6%. The calibration curve was linear with a correlation coefficient of 0.999 over the concentration range 10–5000 ng/mL and the lower limit of quantification was 10 ng/mL. The intra‐ and inter‐day precisions were <11.8%, while the accuracy ranged from 99.6 to 109.0%. A stability study of flomoxef revealed that it could be successfully analyzed at 4ºС over 24 h, but it was unstable in solutions at room temperature during short‐term storage (4 h) and several freeze–thaw cycles. Copyright © 2013 John Wiley & Sons, Ltd.     

Liquid chromatography/tandem mass spectrometry method for quantification of trans-stilbene glycoside in rat plasma and its pharmacokinetic application

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the quantification of trans‐stilbene glycoside (SG) in rat plasma. As trans‐SG can be rapidly isomerized under light exposure, trans‐SG plasma samples were prepared in the dark and assayed immediately. Trans‐SG and internal standard were extracted by protein precipitation. Chromatographic separation was achieved on a C₁₈ column with a gradient elution program. The detection of analytes was performed by negative ion via multiple reaction monitoring mode. The precursor‐to‐product ions of m/z 405.1 → 242.9 for trans‐SG and m/z 389.1 → 226.9 for polydatin (internal standard) were monitored. No interference of endogenous components was observed for any plasma samples that we studied.The method was linear over the concentration range of 1.0–1000.0 ng/mL with a good correlation coefficient. The lower limit of quantification was 1.0 ng/mL for trans‐SG. The intra and inter‐batch accuracy for trans‐SG in stable rat plasma samples ranged from 93.3 to 102.7% and the variation was less than 8.1%. The extraction recoveries of trans‐SG in rat plasma were from 102.8 to 112.4% and the matrix effects were also acceptable. This method was successfully applied to pharmacokinetic study of trans‐SG in rats after intravenous administration. Copyright © 2012 John Wiley & Sons, Ltd.     

Liquid chromatography–tandem mass spectrometric assay for the determination of vaccarin in rat plasma: application to a pharmacokinetic study

Vaccarin, a flavonoid glycoside, is considered one of the major active constituents of Vaccaria segetalis. A simple and specific liquid chromatography–tandem mass spectrometric method was developed and validated for quantifying vaccarin in rat plasma following intravenous dosing. Plasma samples were precipitated with methanol and separated on a Venusil‐C₁₈ analytical column (2.1 × 50 mm, 5 µm particles) with gradient elution consisting of methanol and 0.1% (v/v) formic acid as the mobile phase. The detection was performed on an Agilent Triple Quad LC/MS with electrospray ionization inlet in the positive multiple reaction monitoring mode. Good linearity was achieved over the concentration range of 12.5–25,000 ng/mL (r² > 0.99). Intra‐ and inter‐day precisions were <9.1%, and accuracy ranged from ?2.8 to 8.7%. The lower limit of quantification for vaccarin was 12.5 ng/mL, and the analyte was stable under various storage conditions. This validated method was successfully applied to the preliminary pharmacokinetic studies of vaccarin following intravenous administrations of 1.21, 2.41, and 4.82 mg/kg vaccarin in rats. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of fenofibric acid in human plasma by ultra performance liquid chromatography–electrospray ionization mass spectrometry: application to a bioequivalence study

A rapid, specific and sensitive ultra‐performance liquid chromatography tandem mass spectrometry method was developed for the determination of fenofibric acid in human plasma. The method involves simple, one‐step liquid–liquid extraction procedure coupled with an Acquity UPLC^TM BEH C₁₈ column (50 × 2.1 mm, i.d., 1.7 µm) with isocratic elution at a flow‐rate of 0.2 mL/min and mefenamic acid was used as the internal standard. The Quattro Premier XE mass spectrometry was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. Using 250 µL plasma, the methods were validated over the concentration rang 0.05–7.129 µg/mL, with a lower limit of quantification of 0.05 µg/mL. The intra‐ and inter‐day precision and accuracy were within 9.3%. The recovery was 66.7% and 52.6% for fenofibric acid, and mefenamic acid, respectively. Total run time was 1.8 min only for each sample, which makes it possible to analyze more than 350 samples per day. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of pseudo‐ginsenoside GQ in human plasma by high performance liquid chromatography–tandem mass spectrometry

A specific, sensitive and rapid method based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC‐MS/MS) was developed for the determination of pseudo‐ginsenoside GQ in human plasma. Liquid–liquid extraction was used to isolate the analyte from biological matrix followed by injection of the extracts onto a C₈ column with isocratic elution. Detection was carried out on a triple quadrupole tandem mass spectrometer (API‐4000 system) in multiple reaction monitoring mode using negative electrospray ionization. The mobile phase consisted of methanol–10 mm ammonium acetate (90:10, v/v) and the flow rate was 0.3 mL/min. The method was validated over the concentration range of 5.0–5000.0 ng/mL for plasma. Inter‐ and intra‐day precisions (relative standard deviation) were all within 15% and the accuracy (relative error) was ≤9.4%. The lower limit of quantitation was 5.0 ng/mL. The pseudo‐ginsenoside GQ was stable after 8 h at room temperature, 24 h at autosampler and three freeze–thaw cycles (from ?30 to 25 °C). The method was successfully applied to the pharmacokinetic study of pseudo‐ginsenoside GQ in healthy Chinese volunteers. Copyright © 2013 John Wiley & Sons, Ltd.     

Liquid chromatography tandem mass spectrometry pharmacokinetic study of DL-praeruptorin A in rat plasma

dl ‐Praeruptorin A is a novel drug with valuable apoptosis and inflammation inhibitory effects in cardiac muscle. Previous pharmacokinetic studies of dl ‐praeruptorin A have had limited success due to its very low plasma concentrations. In this study, we developed and validated a new rapid, sensitive and specific high‐performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC/ESI–MS/MS) method for quantitative analysis of dl ‐praeruptorin A in rat plasma. dl ‐Praeruptorin A and diazepam (internal standard) extracted from rat plasma samples with chloroform and analyzed on an XTerra? RP₁₈ column (150 mm × 4.6 mm i.d., 5 µm) were chromatographically separated within 5.5 min using methanol–water (75:25, v/v; flow rate 1 mL/min) as the mobile phase. dl ‐Praeruptorin A was detected in positive ion mode using multiple reaction monitoring. The method was validated and the specificity, linearity, lower limit of quantitation (LLOQ, 2.5 ng/mL), precision (intra‐ and inter‐day <11.0%), accuracy (90.2–96.3%), recovery (>79.2%) and stability were determined. The correlation coefficient (r²) for the linear range of 2.5–2500.0 ng/mL was >0.999. No matrix effects were observed. The validated method was successfully applied to pharmacokinetic studies of dl ‐praeruptorin A after intravenous administration to rats. The LLOQ obtained with this method was lower than in previous studies and could be valuable for determination of dl ‐praeruptorin A in therapeutic drug monitoring and preclinical studies to establish appropriate dose and frequency. Copyright © 2010 John Wiley & Sons, Ltd.     

Simultaneous determination of propofol and remifentanil in rat plasma by liquid chromatography–tandem mass spectrometry: application to preclinical pharmacokinetic drug–drug interaction analysis

Propofol (Pro) is an ultra‐short‐acting hypnotic agent used for general anesthesia that has no analgesic properties. Remifentanil (Rem) is an ultra‐short‐acting opioid administered concomitantly as an analgesic with Pro. To evaluate the pharmacokinetic interactions between Pro and Rem, we developed and validated a method combining high‐performance liquid chromatography with tandem mass spectrometry for simultaneous determination of Pro and Rem. The proposed method was successfully used to study the pharmacokinetic interactions of Pro and Rem coadministered to rats. Copyright © 2014 John Wiley & Sons, Ltd.