Determination of metoprolol enantiomers in human plasma and saliva samples utilizing microextraction by packed sorbent and liquid chromatography–tandem mass spectrometry

A sensitive, accurate and reliable bioanalytical method for the enantioselective determination of metoprolol in plasma and saliva samples utilizing liquid chromatography–electrospray ionization tandem mass spectrometry was developed and validated. Human plasma and saliva samples were pretreated by microextraction by packed sorbent (MEPS) prior to analysis. A new MEPS syringe form with two inputs was used. Metoprolol enantiomers and internal standard pentycaine (IS) were eluted from MEPS sorbent using isopropanol after removal of matrix interferences using aliquots of 5% methanol in water. Complete separation of metoprolol enantiomers was achieved on a Cellulose‐SB column (150 × 4.6 mm, 5 μm) using isocratic elution with mobile phase 0.1% ammonium hydroxide in hexane–isopropanol (80:20, v/v) with a flow rate of 0.8 mL/min. A post‐column solvent‐assisted ionization was applied to enhance metoprolol ionization signal in positive mode monitoring (+ES) using 0.5% formic acid in isopropanol at a flow rate of 0.2 mL/min. The total chromatographic run time was 10 min for each injection. The detection of metoprolol in plasma and saliva samples was performed using triple quadrupole tandem mass spectrometer in +ES under the following mass transitions: m/z 268.08 → 72.09 for metoprolol and m/z 303.3 → 154.3 for IS. The linearity range was 2.5–500 ng/mL for both R‐ and S‐metoprolol in plasma and saliva. The limits of detection and quantitation for both enantiomers were 0.5 and 2.5 ng/mL respectively, in both matrices (plasma and saliva). The intra‐ and inter‐day precisions were presented in terms of RSD values for replicate analysis of quality control samples and were <5%; the accuracy of determinations varied from 96 to 99%. The method was able to determine the therapeutic levels of metoprolol enantiomers in both human plasma and saliva samples successfully, which can aid in therapeutic drug monitoring in clinical laboratories. Copyright © 2016 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.     

Quantification and pharmacokinetics of crizotinib in rats by liquid chromatography–tandem mass spectrometry

Crizotinib is a small molecule inhibitor of anaplastic lymphoma kinase (ALK) and can be used to treat ALK‐positive nonsmall‐cell lung cancer. A rapid and simple high‐performance liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the quantification of crizotinib in rat plasma using a chemical synthetic compound buspirone as the internal standard (IS). The plasma samples were pretreated by a simple protein precipitation with methanol–acetonitrile (1:1, v/v). Chromatographic separation was successfully achieved on an Agilent Zorbax XDB C₁₈ column (2.1 × 50 mm, 3.5 µm). The gradient elution system was composed of 0.1% formic acid aqueous solution and 0.1% formic acid in methanol solution. The flow rate was set at 0.50 mL/min. The multiple reaction monitoring was based on the transitions of m/z = 450.3 → 177.1 for crizotinib and 386.2 → 122.2 for buspirone (IS). The assay was successfully validated to demonstrate the selectivity, matrix effect, linearity, lower limit of quantification, accuracy, precision, recovery and stability according to the international guidelines. The lower limit of quantification was 1.00 ng/mL in 50 μL of rat plasma. This LC‐MS/MS assay was successfully applied to the quantification and pharmacokinetic study of crizotinib in rats after intravenous and oral administration of crizotinib. The oral absolute bioavailability of crizotinib in rats was 68.6 ± 9.63%. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of matrix effects in analysis of estrogen using liquid chromatography–tandem mass spectrometry

Matrix effects of different biological samples, including phosphate‐buffered saline–bovine serum albumin (PBS‐BSA), gelded horse serum, mouse serum, and mouse brain, were investigated for the determination of 17α‐ and β‐estradiol using derivatization with dansyl chloride prior to LC‐MS/MS. Matrix effects were evaluated based on the slopes of regression lines plotted from results obtained in biological matrices versus pure standard solutions. Such plots indicate the enhancement or suppression of signal based on the presence of a particular biological fluid for a particular method. The matrix effects from PBS‐BSA were similar to those of mouse serum. In contrast, analyses performed from horse serum and mouse brain yielded significant ion suppression, especially for 17β‐estradiol. Precipitation during derivatization was observed when pre‐concentrated samples were processed with ethyl acetate as an extraction solvent. This was overcome with the use of methyl tert‐butyl ether; however, matrix effects from this preparation were still present, evidenced by signal suppression and poor linearity in the standard curve. This work affirms that caution should be taken in the transfer of methods for use with different biological matrices, especially in the case where surrogate matrices are necessary for calibration purposes.     

Reliable and sensitive determination of dutasteride in human plasma by liquid chromatography–tandem mass spectrometry

An accurate and precise method was developed and validated using LC‐MS/MS to quantify dutasteride in human plasma. The analyte and dutasteride‐13C6 as internal standard (IS) were extracted from 300 μL plasma volume using methyl tert‐butyl ether–n‐hexane (80:20, v/v). Chromatographic analysis was performed on a Gemini C₁₈ (150 × 4.6 mm, 5 µm) column using acetonitrile–5 mm ammonium formate, pH adjusted to 4.0 with formic acid (85:15, v/v) as the mobile phase. Tandem mass spectrometry in positive ionization mode was used to quantify dutasteride by multiple reaction monitoring. The entire data processing was done using Watson LIMS^TM software, which provided excellent data integrity and high throughput with improved operational efficiency. The calibration curve was linear in the range of 0.1–25 ng/mL, with intra‐and inter‐batch values for accuracy and precision (coefficient of variation) ranging from 95.8 to 104.0 and from 0.7 to 5.3%, respectively. The mean overall recovery across quality controls was ≥95% for the analyte and IS, while the interference of matrix expressed as IS‐normalized matrix factors ranged from 1.01 to 1.02. The method was successfully applied to support a bioequivalence study of 0.5 mg dutasteride capsules in 24 healthy subjects. Assay reproducibility was demonstrated by reanalysis of 103 incurred samples. Copyright © 2013 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 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.     

Rapid and simple determination of psychotropic phenylalkylamine derivatives in urine by direct injection liquid chromatography–electrospray ionization–tandem mass spectrometry

A direct injection liquid chromatography–electrospray ionization–tandem mass spectrometric method (LC‐ESI‐MS/MS) was developed and validated for the rapid and simple determination of 13 phenylalkylamine derivatives. Eight deuterium‐labeled compounds were prepared for use as internal standards (ISs) to quantify the analytes. Urine samples mixed with ISs were centrifuged, filtered through 0.22 µm filters and then injected directly into the LC‐ESI‐MS/MS system. The mobile phase was composed of 0.2% formic acid and 2 mM ammonium formate in distilled water and 0.2% formic acid and 2 mM ammonium formate in acetonitrile. The analytical column was a Capcell Pak MG‐II C₁₈ (150 × 2.0 mm i.d., 5 µm, Shiseido). Separation and detection of the analytes were accomplished within 10 min. The linear ranges were 5–750 ng/mL (ephedrine and fenfluramine), 10–750 ng/mL (3,4‐methylenedioxyamphetamine, phendimetrazine, methamphetamine, 3,4‐methylenedioxyethylamphetamine and benzphetamine), 20–750 ng/mL (norephedrine, amphetamine, phentermine and ketamine) and 30–1000 ng/mL (3,4‐methylenedioxymethamphetamine and norketamine), with determination coefficients, R², ≥ 0.9967. The intra‐day and inter‐day precisions were within 19.1%. The intra‐day and inter‐day accuracies ranged from ?16.0 to 18.7%. The lower limits of quantification for all the analytes were lower than 26.5 ng/mL. The applicability of the method was examined by analyzing urine samples from drug abusers (n = 30). Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of dopamine and serotonin in human urine samples utilizing microextraction online with liquid chromatography/electrospray tandem mass spectrometry

A specific LC-MS-MS method for the determination of dopamine and serotonin (5-hydroxytryptamine; 5HT) in human urine is described. The analytes were extracted from urine and preconcentrated by microextraction in a packed syringe (MEPS). The new method is very promising, very easy to use, fully automated, of low cost, and rapid in comparison to previously used methods. The method was validated and the standard curves were evaluated by means of quadratic regression and weighted by inverse of the concentration: 1/x for the calibration range 50-4000 microg/L. The MEPS applied polymer (silica-C8) could be used more than 300 times. The extraction recovery was about 50%. The results showed close correlation coefficients (r2 > 0.999) for all analytes in the calibration range studied. The accuracy of MEPS-LC-MS-MS was 100-101% for dopamine and 99-100% for 5HT. The interday precision (n = 3 days), expressed as the RSD%, was 6.0-7.7% for dopamine and 6.1-11% for 5HT. MEPS reduced the handling time by 12 times compared to a published method.     

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 L‐ergothioneine in human plasma and erythrocytes by liquid chromatography‐tandem mass spectrometry

A sensitive analytical method has been developed and validated for the quantification of L‐ergothioneine in human plasma and erythrocytes by liquid chromatography‐tandem mass spectrometry. A commercially available isotope‐labeled L‐ergothioneine‐d₉ is used as the internal standard. A simple protein precipitation with acetonitrile is utilized for bio‐sample preparation prior to analysis. Chromatographic separation of L‐ergothioneine is conducted using gradient elution on Alltime C18 (150 mm × 2.1 mm, 5 µ). The run time is 6 min at a constant flow rate of 0.45 ml/min. The mass spectrometer is operated under a positive electrospray ionization condition with multiple reaction monitoring mode. The mass transitions of L‐ergothioneine and L‐ergothioneine‐d₉ are m/z 230 > 127 and m/z 239 > 127, respectively. Excellent linearity [coefficient of determination (r²) ≥ 0.9998] can be achieved for L‐ergothioneine quantification at the ranges of 10 to 10 000 ng/ml, with the intra‐day and inter‐day precisions at 0.9–3.9% and 1.3–5.7%, respectively, and the accuracies for all quality control samples between 94.5 and 101.0%. This validated analytical method is suitable for pharmacokinetic monitoring of L‐ergothioneine in human and erythrocytes. Based on the determination of bio‐samples from five healthy subjects, the mean concentrations of L‐ergothioneine in plasma and erythrocytes are 107.4 ± 20.5 ng/ml and 1285.0 ± 1363.0 ng/ml, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous determination of 14 constituents of Radix polygoni multiflori from different geographical areas by liquid chromatography–tandem mass spectrometry

Radix polygoni multiflori (RPM) has antioxidative, anti‐aging, liver‐protective and antihuman cytomegalovirus activity. It has been proved to be hepatotoxic. Considering multiple ingredients to control RPM quality is essential. The aim of this study was to establish a simple, rapid method using resolution liquid chromatography coupled with a triple quadruple mass spectrometry to identify and quantify the major bioactive constituents in RPM. The method was applied to analyze 14 marker batches from manufacturers from the same province. The ultrasonic extracts of all samples were determined by LC‐MS/MS, and assessed by hierarchical cluster analysis. The proposed method was applied to analyze 21 batches of samples with acceptable linearity (R², 0.9930–0.9998), precision (relative standard deviation, RSD, 0.45–4.73%) repeatability (RSD, 1.14–9.41%), stability (RSD, 1.29–12.88%) and recovery (RSD, 1.80–12.15%) of the 14 compounds. Furthermore, the hierarchical cluster analysis was applied to classify 21 samples on the basis of characteristics of the 14 compound markers. The developed method was demonstrated to be simple, sensitive and reproducible, and has significant importance and comprehensive evaluation for quality control of RPM and related preparations. Hierarchical cluster analysis clearly indicated that the RPM from the same province was similar, whereas samples of RPM from different provinces were significantly different. Copyright © 2014 John Wiley & Sons, Ltd.     

Molecularly imprinted polymer in microextraction by packed sorbent for the simultaneous determination of local anesthetics: lidocaine,ropivacaine, mepivacaine and bupivacaine in plasma and urine samples

This study presents the use of molecularly imprinted polymer (MIP) as packing material for microextraction by packed syringe (MEPS) to achieve higher extraction selectivity. Pentycaine was used as template for MIP. Development and validation of the determination of lidocaine, ropivacaine, mepivacaine and bupivacaine in human plasma and urine samples utilizing MIP‐MEPS and liquid chromatography–tandem mass spectrometry (LC‐MS/MS) were carried out. The MEPS MIP‐cartridge could be used for 100 extractions before it was discarded. The extraction recovery ranged from 60 to 80%. The correlation coefficients values were >0.999 for all assays using lidocaine, ropivacaine, mepivacaine and bupivacaine in the calibration range 5–2000 nmol/L. The accuracy of the studied compounds, given as a percentage variation from the nominal concentration values, ranged from ‐4.9 to 8.4% using plasma and urine samples. The between‐batch precision, given as the relative standard deviation, at three different concentrations (quality control samples) was ranged from ?4.7 to 14.0% and from 1.8 to 12.7% in plasma and urine, respectively. The lower limit of quantification and limit of detection of the studied substances were 5.0 and 1.0 nm , respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantification and pharmacokinetics of Taiwanin E methyl ether in rats by liquid chromatography–tandem mass spectrometry

This study firstly describes the development of an accurate and sensitive high‐performance liquid chromatography–tandem mass spectrometry (LC‐MS/MS) assay for the quantification of Taiwanin E methyl ether (TEME) in rat plasma. The assay involved a simple liquid–liquid extraction step with ethyl acetate and a gradient elution using a mobile phase consisting of water containing 0.1% formic acid and acetonitrile containing 0.1% formic acid. Chromatographic separation was successfully achieved on an Agilent Zorbax‐C₁₈ column (2.1 × 50 mm, 3.5 µm) with a flow rate of 0.40 mL/min. The multiple reaction monitoring was based on the transitions of m/z = 379.1 → 320.1 for TEME and 386.1 → 122.0 for buspirone (internal standard). The assay was validated to demonstrate the specificity, linearity, recovery, accuracy, precision and stability. The lower limit of quantification was 0.50 ng/mL in 50 μL of rat plasma. The developed and validated method was successfully applied to the quantification and pharmacokinetic study of TEME in rats after intravenous and oral administration of 1.45 mg/kg TEME. The oral absolute bioavailability of TEME was estimated to be 5.85 ± 1.41% with an elimination half‐life value of 2.61 ± 0.55 h, suggesting its poor absorption and/or strong metabolism in vivo. Copyright © 2012 John Wiley & Sons, Ltd.     

Simultaneous determination of erlotinib and its isomeric major metabolites in human plasma using isocratic liquid chromatography–tandem mass spectrometry and its clinical application

This study developed a method for the simultaneous determination of erlotinib and its isomeric major metabolites, OSI‐413 and OSI‐420, in human plasma using an isocratic liquid chromatography–tandem mass spectrometry. Plasma specimens deproteinized with acetonitrile were separated using a 3‐µm particle size octadecylsilyl column. The m/z values of the precursor and product ions for the analytes were as follows: erlotinib, 394.2/278.2; and OSI‐413 and OSI‐420, 380.2/278.2. The total run time was 21 min and no peaks interfering with the analytes and internal standard (d₆‐erlotinib) in human plasma were observed. The calibration curves of erlotinib, OSI‐413 and OSI‐420 were linear over the concentration ranges of 10–3000, 2–500 and 2–100 ng/mL, respectively. The pretreatment recovery ratios were >86.1%. The intra‐ and inter‐assay precisions and accuracies were <12.7 and 89.0–108.9% for all analytes. This validated method was applied to the determination of plasma samples in lung cancer patients receiving 150 mg of oral erlotinib. The plasma concentration ranges of erlotinib, OSI‐413 and OSI‐420 were 373–2354, 15.7–379 and 2.5–43.6 ng/mL, respectively. In conclusion, the present method can be helpful for evaluating the plasma exposures of erlotinib and its major isomeric metabolites in clinical settings. Copyright © 2014 John Wiley & Sons, Ltd.     

Sensitive and selective liquid chromatography–tandem mass spectrometry method for the determination of metoclopramide in human plasma: application to a bioequivalence study

A simple, sensitive and rapid method has been developed and validated for determination of the metoclopramide (MCP) in 100 μL human plasma. The analytical procedure involves a liquid–liquid extraction method using tramadol as an internal standard (IS). Chromatographic separation was carried out on a HyPURITY ADVANCE column using a mobile phase consisting of acetonitrile and 10 mm ammonium acetate buffer in the ratio of 80:20 (v/v) at a flow rate of 0.3 mL/min. The total run time of analysis was 2.5 min and elution of MCP and IS occurred at 0.9 and 1.3 min, respectively. A linear response function was established for the range of concentrations 0.53–42.07 ng/mL (r > 0.99). The intra‐ and inter‐day precision values for MCP met the acceptance as per FDA guidelines. MCP was stable in a battery of stability studies viz., bench‐top, auto‐sampler and freeze–thaw cycles. The developed assay method was successfully applied to an oral bioequivalence study in humans. 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.     

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.     

A simple,rapid and sensitive liquid chromatography–tandem mass spectrometry method for the determination of dienogest in human plasma and its pharmacokinetic applications under fasting

A simple, rapid and sensitive analytical method using liquid chromatography coupled to tandem mass spectrometry (LC‐MS/MS) detection with positive ion electrospray ionization was developed for the determination of dienogest in human K₂EDTA plasma using levonorgestrel d₆ as an internal standard (IS). Dienogest and IS were extracted from human plasma using simple liquid–liquid extraction. Chromatographic separation was achieved on a Zorbax XDB‐Phenyl column (4.6 × 75 mm, 3.5 µm) under isocratic conditions using acetonitrile–5 mm ammonium acetate (70:30, v/v) at a flow rate of 0.60 mL/min. The protonated precursor to product ion transitions monitored for dienogest and IS were at m/z 312.30 → 135.30 and 319.00 → 251.30, respectively. The method was validated with a linearity range of 1.003–200.896 ng/mL having a total analysis time for each chromatograph of 3.0 min. The method has shown tremendous reproducibility with intra‐ and inter‐day precision (coefficient of variation) <3.97 and 6.10%, respectively, and accuracy within ±4.0% of nominal values. The validated method was applied to a pharmacokinetic study in human plasma samples generated after administration of a single oral dose of 2.0 mg dienogest tablets to healthy female volunteers and was proved to be highly reliable for the analysis of clinical samples. Copyright © 2014 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.