Development and validation of LC–MS/MS method for quantification of bictegravir in human plasma and its application to an intracellular uptake study

A sensitive liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for quantification of bictegravir in human plasma. A small volume of only 50 μL aliquot of plasma was precipitated with acetonitrile containing an internal standard (IS). Chromatographic separation was performed on a Kinetex EVO C₁₈ column, 50 × 3.0 mm, 5 μm using an isocratic mobile phase containing 80:20 acetonitrile–water with 0.1% formic acid. A mass spectrometer was operated in ESI positive multiple reaction monitoring mode using the m/z 450.1/289.1 for bictegravir and 420.1/277.1 for IS. The dynamic range of the method was 1–10,000 ng/mL with a correlation coefficient of ≥0.9991. The precision results of calibration standards were in the range of 0.05–4.57% and accuracies were 95.07–104.70%. The mean extraction recovery was 98.64% with a precision of 2.91%. The method was validated as per US Food and Drug Administration guidelines and was found to be accurate and precise. The method was successfully applied to in vitro cellular uptake study.     

Comparative pharmacokinetics of acteoside from total glycoside extracted from leaves of Rehmannia and Dihuangye total glycoside capsule in normal and diabetic nephropathy rats

Rehmannia glutinosa Libosch (RG), is officially listed in the Chinese Pharmacopoeia and is widely used in China. In this paper, a sensitive and rapid ultra‐performance liquid chromatography–mass spectrometry method including multiple‐reaction monitoring mode was developed and applied to study the pharmacokinetic effect of acteoside from total glycoside extracted from the leaves of Rehmannia (TLR) and Dihuangye total glycoside capsule (DTG) in normal and diabetic nephropathy rats. The diabetic nephropathy rat model was induced by intraperitoneal injection of a small dose of streptozotocin and high‐fat diet and plus 5% glucose drinking water. Samples of plasma of rats were obtained at different times after rats were administered TLR (7.2 g/kg) and DTG (360 mg/kg). After deproteinization by acetonitrile, the concentrations of acteoside in rats at different time points were detected by UPLC‐TQ‐MS method and pharmacokinetics parameters were calculated using DAS 3.2.8 software. A good linearity of acteoside was shown in the range of 8.51–3404.8 ng/m L (r ² = 0.9987). The mean extraction recovery of analyte was in the range of 63.55–79.49%, and the intra‐ and inter‐day RSD values were <8.8%. Compared with the normal group, the maximum plasma concentration, AUC_0–t , AUC_0–∞ and apparent plasma clearance corresponding dose in model group rats decreased significantly. After rats were administered TLR and DTG, the acteoside reached the maximum plasma concentration at about 15 min. The method proved to be simple, rapid and specific, and to be suitable for the determination of acteoside in plasma of diabetic nephropathy rats and pharmacokinetic study.     

Development and validation of LC‐MS/MS method for the estimation of β‐hydroxy‐β‐methylbutyrate in rat plasma and its application to pharmacokinetic studies

A simple, sensitive and specific high‐performance liquid chromatography mass spectrometry (LC‐MS/MS) method was developed and validated for the quantification of β‐hydroxy‐β‐methyl butyrate (HMB) in small volumes of rat plasma using warfarin as an internal standard (IS). The API‐4000 LC‐MS/MS was operated under the multiple reaction‐monitoring mode using the electrospray ionization technique. A simple liquid–liquid extraction process was used to extract HMB and IS from rat plasma. The total run time was 3 min and the elution of HMB and IS occurred at 1.48 and 1.75 min respectively; this was achieved with a mobile phase consisting of 0.1% formic acid in a water–acetonitrile mixture (15:85, v/v) at a flow rate of 1.0 mL/min on a Agilent Eclipse XDB C₈ (150 × 4.6, 5 µm) column. The developed method was validated in rat plasma with a lower limit of quantitation of 30.0 ng/mL for HMB. A linear response function was established for the range of concentrations 30–4600 ng/mL (r > 0.998) for HMB. The intra‐ and inter‐day precision values for HMB were acceptable as per Food and Drug Administration guidelines. HMB was stable in the battery of stability studies, viz. bench‐top, autosampler freeze–thaw cycles and long‐term stability for 30 days in plasma. The developed assay method was applied to a bioavailability study in rats. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of a liquid chromatography–tandem mass spectrometry method for the determination of febuxostat in human plasma

A rapid and sensitive analytical method based on liquid chromatography coupled to tandem mass spectrometry detection with positive ion electrospray ionization was developed for the determination of febuxostat in human plasma using d₇‐febuxostat as the internal standard (IS). A simple protein precipitation was performed using acetonitrile. The analyte and IS were subjected to chromatographic analysis on a Capcell PAK C₁₈ column (4.6 × 100 mm, 5 µm) using acetonitrile–5 mm ammonium acetate–formic acid (85:15:0.015, v/v/v) as the mobile phase at a flow rate of 0.6 mL/min. An Agilent 6460 electrospray tandem mass spectrometer was operated in the multiple reaction monitoring mode. The precursor‐to‐product ion transitions m/z 317 → m/z 261 (febuxsotat) and m/z 324 → m/z (261 + 262) (d₇‐febuxostat, IS) were used for quantitation. The results were linear over the studied range (10.0–5000 ng/mL), and the total analysis time for each chromatograph was 3 min. The intra‐ and inter‐day precisions were less than 7.9 and 7.2%, respectively, and the accuracy was within ±4.2%. No evidence of analyte instability in human plasma was observed storage at ?20°C for 31 days. This method was successfully applied in the determination of febuxostat concentrations in plasma samples from healthy Chinese volunteers. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of Armillarisin A in Rat Plasma by SPE and LC-MS-MS

A rapid, sensitive and convenient ultra-performance liquid chromatography-tandem mass spectrometry method was developed and validated for the determination of armillarisin A in rat plasma. Following hydrophilic–lipophilic balance solid-phase extraction, armillarisin A and propylparaben (internal standard) were separated using a gradient elution program on a C₁₈ column and detected by mass spectrometry in the negative ion mode with the multiple reaction monitoring mode. The total chromatographic running time was short (1.8 min). The method was linear over the concentration range of 0.5–250.00 ng mL^?1 for armillarisin A. The lower limit of quantification of armillarisin A was 0.5 ng mL^?1, using as little as 100 μL plasma. The intra-day and inter-day relative standard deviations were less than 15% and the relative errors were all within 10%. The extraction recovery for armillarisin A was approximately 100%, and no absolute matrix effect was observed. Finally, the method was successfully applied to a preclinical pharmacokinetic study of armillarisin A in four rats following an intravenous administration.     

Simultaneous determination of tandospirone and its active metabolite, 1‐[2‐pyrimidyl]‐piperazine in rat plasma by LC–MS/MS and its application to a pharmacokinetic study

A rapid, sensitive and selective liquid chromatography–tandem mass spectrometry method for the detection of tandospirone (TDS) and its active metabolite 1‐[2‐pyrimidyl]‐piperazine (1‐PP) in Sprague–Dawley rat plasma is described. It was employed in a pharmacokinetic study. These analytes and the internal standards were extracted from plasma using protein precipitation with acetonitrile, then separated on a CAPCELL PAK ADME C₁₈ column using a mobile phase of acetonitrile and 5 mm ammonium formate acidified with formic acid (0.1%, v/v) at a total flow rate of 0.4 mL/min. The detection was performed with a tandem mass spectrometer equipped with an electrospray ionization source. The method was validated to quantify the concentration ranges of 1.000–500.0 ng/mL for TDS and 10.00–500.0 ng/mL for 1‐PP. Total time for each chromatograph was 3.0 min. The intra‐day precision was between 1.42 and 6.69% and the accuracy ranged from 95.74 to 110.18% for all analytes. Inter‐day precision and accuracy ranged from 2.47 to 6.02% and from 98.37 to 105.62%, respectively. The lower limits of quantification were 1.000 ng/mL for TDS and 10.00 ng/mL for 1‐PP. This method provided a fast, sensitive and selective analytical tool for quantification of tandospirone and its metabolite 1‐PP in plasma necessary for the pharmacokinetic investigation.     

Determination of meloxicam in human plasma by ultra-high-performance liquid chromatography–tandem mass spectrometry and its application in a pharmacokinetic study

A rapid, selective and sensitive ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method was developed to detect meloxicam in human plasma. A triple quadrupole tandem mass spectrometer equipped with an electrospray ionization source was used in positive ion mode. Protein precipitation with acetonitrile was used for sample preparation. Meloxicam and ¹³C₆-meloxicam internal standard were analyzed on an Acquity CSH C₁₈ column with a mobile phase of acetonitrile and water in 0.1% formic acid using a gradient program for separation. The retention time of meloxicam was 1.1 min and the total run time was only 2.0 min. Detection was performed in multiple reaction monitoring mode using an electrospray ionization source with optimized mass spectrometry parameters. The calibration curves were linear in the range 10.0–3.00 × 10³ ng/ml (r ≥ 0.99). The within-run and between-run RSDs were ≤14.8%. The within-run and between-run REs ranged from −4.6 to 10.7%. There was no significant matrix effect, and the recovery rate was high. This method was fully validated, including reinjection reproducibility in human plasma. The method was applied to the pharmacokinetic study. All of the incurred sample reanalysis methods met the criteria.     

Highly sensitive method for the determination of adenosine by LC-MS/MS-ESI: method validation and scope of application to a pharmacokinetic/pharmacodynamic study

A highly sensitive, rapid assay method has been developed and validated for the estimation of adenosine in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electro‐spray ionization in the positive‐ion mode. The assay procedure involves extraction of adenosine and phenacetin (internal standard, IS) from rat plasma with a simple protein precipitation extraction process. The method was validated using rat plasma with extinguished adenosine endogenous levels. Chromatographic separation was achieved using a binary gradient using mobile phase A (acetonitrile) and B (0.2% formic acid in water) at a flow rate of 0.50 mL/min on an Atlantis dC₁₈ column with a total run time of 4.0 min. The MS/MS ion transitions monitored were 268 → 136 for adenosine and 180 → 110 for IS. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.48 ng/mL and the linearity range extended from 0.48 to 1210 ng/mL. The intra‐ and inter‐day precisions were in the ranges 2.32–12.7 and 4.01–9.40%, respectively. Copyright © 2011 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.     

A robust and rapid liquid chromatography tandem mass spectrometric method for the quantitative analysis of 5‐azacytidine

The DNA methyltransferase inhibitor 5‐azacytidine is being evaluated clinically as an oral formulation to treat various solid tumors. A sensitive, reliable method was developed to quantitate 5‐azacytidine using LC‐MS/MS to perform detailed pharmacokinetic studies. The drug of interest was extracted from plasma using Oasis MCX ion exchange solid‐phase extraction 96‐well plates. Chromatographic separation was achieved with a YMC J'sphere M80 C₁₈ column and isocratic elution with a methanol–water–formic acid (15:85:0.1, v/v/v) mobile phase over a 7 min total analytical run time. An AB Sciex 5500 triple quadrupole mass spectrometer operated in positive electrospray ionization mode was used for the detection of 5‐azacytidine. The assay range was 5–500 ng/mL and proved to be accurate (97.8–109.1%) and precise (CV ≤ 9.8%). Tetrahydrouridine was used to stabilize 5‐azacytidine in blood/plasma samples. With the addition of tetrahydrouridine, long‐term frozen plasma stability for 5‐azacytidine at ?70°C has been determined for at least 323 days. The method was applied for the measurement of total plasma concentrations of 5‐azacytidine in a cancer patient receiving a 300 mg oral daily dose. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitation of unbound sunitinib and its metabolite N-desethyl sunitinib (SU12662) in human plasma by equilibrium dialysis and liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study

A rapid, selective, and sensitive liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous determination of unbound sunitinib and its active metabolite N‐desethyl sunitinib in plasma. Plasma and post‐dialysis buffer samples were extracted using a liquid–liquid extraction procedure with acetonitrile–n‐butylchloride (1:4, v/v). Chromatographic separation was achieved on a Waters X‐Terra® MS RP₁₈ column with a mobile phase consisting of acetonitrile and water (60:40, v/v) containing formic acid (0.1%, v/v) using an isocratic run, at a flow‐rate of 0.2 mL/min. Analytes were detected by electrospray tandem mass spectrometry in the selective reaction monitoring mode. Linear calibration curves were generated over the ranges 0.1–100 and 0.02–5 ng/mL for sunitinib and 0.2–200 and 0.04–10 ng/mL for N‐desethyl sunitinib in plasma and in phosphate‐buffered solution, respectively. The values for both within‐day and between‐day precision and accuracy were well within the generally accepted criteria for analytical methods. The analytical range was sufficient to determine the unbound and total concentrations of both analytes. The method was applied for measurement unbound concentrations in addition to total concentrations of sunitinib and its metabolite in plasma of a cancer patient receiving 50 mg daily dose. Copyright © 2012 John Wiley & Sons, Ltd.     

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

A sensitive, rapid assay method for estimating ivabradine in human plasma has been developed and validated using liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The procedure involved extraction of ivabradine and the internal standard (IS) from human plasma by solid‐phase extraction. Chromatographic separation was achieved using an isocratic mobile phase (0.1% formic acid–methanol, 60:40, v/v) at a flow rate of 1.0 mL/min on an Aglient Eclipse XDB C₈ column (150 × 4.6 mm, 5 µm; maintained at 35°C) with a total run time of 4.5 min. Detection was achieved using an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 3200 triple‐quadrupole mass spectrometer. The MS/MS ion transitions monitored were 469–177 for ivabradine and 453–177 for IS. Method validation was performed according to Food and Drug Administration guidelines, and the results met the acceptance criteria. The calibration curve was linear over a concentration range of 0.1–200 ng/mL. The lower limit of quantitation achieved was 0.1 ng/mL. Intra‐ and inter‐day precisions were in the range of 1.23–14.17% and 5.26‐8.96%, respectively. Finally, the method was successfully used in a pharmacokinetic study that measured ivabradine levels in healthy volunteers after a single 5 mg oral dose of ivabradine. Copyright © 2013 John Wiley & Sons, Ltd.     

Determination of Ginsenoside Rg2 in Rat Plasma by High‐Performance Liquid Chromatography–Mass Spectrometry after Solid‐Phase Extraction

Abstract

A sensitive liquid chromatography‐mass spectrometric (LC/MS) method for the quantification of ginsenoside Rg2 (Rg2) in rat plasma was developed after solid‐phase extraction (SPE). Chromatographic separation was achieved on a reversed‐phase Kromasil C₁₈ column with the mobile phase of acetonitrile‐ammonium chloride (500 µM/L) and step gradient elution resulted in a total run time of about 9 min. The analytes were detected using electrospray negative ionization mass spectrometry in the selected ion monitoring (SIM) mode. A good linear relationship was obtained in the concentration range (5–2500 ng/mL) (r=0.9999). Limit of quantification (LOQ) was 5 ng/mL and the limit of detection (LOD) was 2 ng/mL using 100 µL plasma sample. Average recoveries ranged from 72.43–84.73% in plasma at the concentrations of 20, 200, and 2000 ng/mL. Intra‐ and interday coefficients of variation for the assay were 4.93–10.87% and 4.06–7.84%, respectively. The method was successfully applied to the analysis of ginsenoside Rg2 in rat plasma. The applicability of this assay was examined in a preliminary pharmacokinetic study of ginsenoside Rg2 in rats.     

Liquid chromatography–electrospray ionization tandem mass spectrometry for the quantification of styraxlignolide A in rat plasma

Styraxlignolide A is a pharmacologically active ingredient isolated from Styrax japonica Sieb. et Zucc. A rapid, selective, and sensitive liquid chromatographic method with electrospray ionization tandem mass spectrometry was developed for use in the quantification of styraxlignolide A in rat plasma. Styraxlignolide A was extracted from rat plasma using ethyl acetate at neutral pH. The analytes were separated on an Atlantis dC₁₈ column using a mixture of methanol and ammonium formate (10 mM, pH 3.0) (70:30, v/v) and detected by tandem mass spectrometry in multiple reaction monitoring mode. The standard curve was linear (r²=0.9978) over the concentration range of 100?10000 ng/mL. The lower limit of quantification was 100 ng/mL using 50 μL of plasma sample. The coefficient of variation and relative error for intra‐ and inter‐assays at four QC levels were 1.6–8.3% and from ?12.0 to ?1.7%, respectively. The present method was applied successfully to the pharmacokinetic study of styraxlignolide A after intravenous administration of styraxlignolide A at a dose of 10 mg/kg in male Sprague–Dawley rats.     

Development of a stable isotope dilution UPLC‐MS/MS method for quantification of dexmedetomidine in a small amount of human plasma

Dexmedetomidine (Dex) is a selective central α2‐agonist with anesthetic properties and has been used in clinical practice for sedation in the intensive care unit (ICU) after operations. In this study, an analytical assay for the determination of Dex in a small amount of plasma was developed for the application to pediatric ICU trials. The quantification of Dex was constructed using the original stable isotope Dex‐d₃ for electrospray ionization‐tandem mass spectrometry (ESI‐MS/MS) in the selected reaction monitoring mode. A rapid ultra‐performance liquid chromatography technique was adopted using ESI‐MS/MS with a runtime of 3 min. Efficacious concentration levels (50 pg/mL to 5 ng/mL) could be evaluated using a very small amount of plasma (10 μL) from patients. The lower limit of the quantification was 5 pg/mL in the plasma (100 µL). For sample preparation, a solid‐phase extraction was used along with the OASIS‐HLB cartridge type. Recovery values ranged from 98.8 to 100.3% for the intra‐ [relative standard deviation (RSD), 0.9–1.3%] and inter‐ (RSD, 0.9–1.5%) day assays. A stable test had recovery values that ranged from 97.8 to 99.7% with an RSD of 1.0–1.9% for the process/wet extract, bench‐top, freeze–thaw and long‐term tests. This method was used to measure the Dex levels in plasma from pediatric ICU patients. In the clinical ICU trial, the small amount of blood (approximate plasma volume, 200 μL) remaining from blood gas analysis was reused and targeted for the clinical analysis of Dex in plasma. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous determination of β‐sitosterol,campesterol, and stigmasterol in rat plasma by using LC–APCI‐MS/MS: Application in a pharmacokinetic study of a titrated extract of the unsaponifiable fraction of Zea mays L.

A liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry method was developed and validated to investigate the pharmacokinetic properties of β‐sitosterol, campesterol, and stigmasterol in rat plasma. Cholesterol‐d₆ was used as an internal standard. To avoid interference of the three phytosterols in rat plasma and minimize matrix effects, a small volume (10 μL) of 4% bovine serum albumin was used as a surrogate matrix for making calibrators and quality control samples. Rat plasma (10 μL) samples were extracted by liquid–liquid extraction with methyl tert‐butyl ether and separated on a Kinetex C₁₈ column. The detection was performed on a triple quadrupole tandem mass spectrometer in selected reaction monitoring mode using positive atmospheric pressure chemical ionization. This assay was linear over concentration ranges of 250–5000 ng/mL (β‐sitosterol), 250–5000 ng/mL (campesterol), and 50–2000 ng/mL (stigmasterol). Additionally, a second set of quality controls made in rat plasma was also evaluated against calibration curves made using the surrogate matrix. All the validation data, including the specificity, precision, accuracy, recovery, matrix effect, stability, and incurred sample reanalysis conformed to the acceptance requirements. Our method was successfully applied to study the pharmacokinetics of three phytosterols in rats.     

Bioanalytical technique for determination of tasimelteon in human plasma by LC–MS/MS and its application to pharmacokinetic study in humans

A highly sensitive, specific and rapid liquid chromatography–tandem mass spectrometry technique for the quantification of tasimelteon in human plasma has been developed and validated using tasimelteon‐d₅ as internal standard. Liquid–liquid extraction technique with ethyl acetate was used for extraction of tasimelteon from the plasma. The chromatographic separation was achieved on an Agilent Zorbax, Eclipse, C₁₈ (4.6 × 50 mm, 5 μm) column using a mobile phase of acetonitrile and 0.02% formic acid buffer (85:15, v/v) with a flow rate of 0.5 mL/min. A detailed method validation was performed as per the United States Food and Drug Administration guidelines. The linear calibration curve was obtained over the concentration range 0.30–299 ng/mL. The API‐4000 liquid chromatography–tandem mass spectrometry was operated under multiple reaction monitoring mode during analysis. The validated method was successfully applied to estimate plasma concentration of tasimelteon after oral administration of a single dose of a 20 mg capsule in healthy volunteers under fasting conditions. The maximum concentration of the drug achieved in the plasma was 314 ± 147 ng/mL and the time at which this concentration was attained was 0.54 ± 0.22 h.     

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.     

A supported liquid extraction LC–MS/MS method for determination of concentrations of GDC‐0425, a small molecule Checkpoint kinase 1 inhibitor,in human plasma

A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the determination of GDC‐0425 concentrations in human plasma has been developed and validated. Supported liquid extraction was used to extract plasma samples (50 μL) and the resulting samples were analyzed using reverse‐phase chromatography and mass spectrometry coupled with a turbo‐ionspray interface. The mass analysis of GDC‐0425 was performed using multiple reaction monitoring transitions in positive ionization mode. The method was validated over the calibration curve range of 1.00–1000 ng/mL using linear regression and 1/x² weighting. Within‐run relative standard deviation ranged from 0.8 to 5.1%, while between‐run RSD varied from 1.9 to 4.7% for QCs. The accuracy ranged from 90.0 to 101.0% of nominal for within‐run and from 94.0 to 100.0% of nominal for between‐run. Overall extraction recovery was 87.4% for GDC‐0425 and 87.9% for GDC‐0425‐d₉. Stability of GDC‐0425 was established in human plasma for 374 days at ?20 and ?70 °C and established in reconstituted sample extracts for 88 h when stored at 2–8 °C. Stable‐labeled internal standard was used to minimize matrix effects. This assay was used to characterize the pharmacokinetics of GDC‐0425 in cancer patients.     

Determination of a novel paclitaxel derivative (NPD‐103) in human plasma by ultra‐performance liquid chromatography–tandem mass spectrometry

A sensitive and specific ultra‐performance liquid chromatography–tandem mass spectrometry (UPLC‐MS‐MS) method for quantification of a newly developed anticancer agent NPD‐103 has been established. An aliquot of human plasma sample (200 µL) was spiked with ¹³C‐labeled paclitaxel (internal standard) and extracted with 1.3 mL of tert‐butyl methyl ether. NPD‐103 was quantitated on a C₁₈ column with methanol–0.1% formic acid (75:25, v/v) as mobile phase using UPLC‐MS‐MS operating in positive electrospray ionization mode with a total run time of 3.0 min. For NPD‐103 at the concentrations of 1.0, 5.0 and 10.0 µg/mL in human plasma, the absolute extraction recoveries were 95.58, 102.43 and 97.77%, respectively. The linear quantification range of the method was 0.1–20.0 µg/mL in human plasma with linear correlation coefficients greater than 0.999. The intra‐ and inter‐day accuracy for NPD‐103 at 1.0, 5.0 and 10.0 µg/mL levels in human plasma fell into the ranges of 95.29–100.00% and 91.04–94.21%, and the intra‐ and inter‐day precisions were in the ranges of 8.96–11.79% and 7.25–10.63%, respectively. This assay is applied to determination of half‐life of NPD‐103 in human plasma. Copyright © 2008 John Wiley & Sons, Ltd.