Validation of rapid and simple LC-MS/MS method for determination of voriconazole in rat plasma

A rapid, simple and sensitive LC-MS/MS analytical method was developed and validated for the determination of voriconazole (VRC) in rat plasma, using ketoconazole as internal standard (IS). Analysis was performed on a Shimadzu HPLC system using a Shimadzu C18 column and isocratic elution with acetonitrile-water-formic acid (60:40:0.05, v/v/v), at a flow of 1.0 mL/min (split ratio 1:5), and a mass spectrometer Micromass, equipped with a double quadrupole and an electrospray ionization interface, operated in a positive mode. Plasma samples were deproteinized with methanol (1:2) and 30 microL of the supernatant was injected into the system. The retention times of VRC and IS were approximately 3.3 and 2.7 min, respectively. Calibration curves in spiked plasma were linear over the concentration range of 50-2500 ng/mL with determination coefficient >0.98. The lower limit of quantification was 50 ng/mL. The accuracy of the method was within 5%. Intra- and inter-day relative standard deviations were less or equal to 12.5 and 7.7%, respectively. The applicability of the LC-MS-MS method for pharmacokinetic studies was tested using plasma samples obtained after intravenous administration of VRC to male Wistar rats. The reported method provided the necessary sensitivity, linearity, precision, accuracy, and specificity to allow the determination of VRC in pre-clinical pharmacokinetic studies.     

Development of a rapid LC-MS/MS method for ribavirin determination in rat brain

A rapid and specific liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the determination of ribavirin (RBV) in rat brain was developed. Sample preparation required only two centrifuge steps before LC-MS/MS analysis and the chromatographic separation was achieved in isocratic conditions using an Atlantis T3 column with a nearly totally aqueous (95%) mobile phase. The method showed a good linearity over a concentration range of 5-1000ppb and satisfactory results in terms of accuracy.     

Determination of the cardioactive prototype LASSBio-294 and its metabolites in dog plasma by LC-MS/MS: application for a pharmacokinetic study

In this work we describe the evaluation of the pharmacokinetics of a novel cardioactive compound of the N-acylhydrazone class, LASSBio-294, using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) in dog plasma for the first time. Separation was achieved on a ZORBAX Rapid Resolution High Definition (RRHD) SB-C18 (50mm×2.1mm, 1.8μm) reversed-phase column at 20°C with methanol-10mM ammonium acetate solution (65:35, v/v) at a flow rate of 1.0mL/min. Detection was performed using an electrospray ionization (ESI) operating in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 275.2→149.1 (LASSBio-294) and m/z 152.0→110.0 (acetaminophen, internal standard). The calibration curve of LASSBio-294 in plasma showed good linearity over the concentration range of 1.25-800ng/mL. The validated method was successfully applied to a pre-clinical pharmacokinetic study of the cardioactive prototype LASSBio-294 in beagles after oral administration. The main pharmacokinetic parameters t(1/2), C(max) and AUC(0-24) were (5.74±0.55)h, (547.66±35.12)ng/mL and (1621.77±41.66)ngh/mL, respectively.     

A rapid LC-MS/MS method for simultaneous determination of quetiapine and duloxetine in rat plasma and its application to pharmacokinetic interaction study

Combinations of new antidepressants like duloxetine and second-generation antipsychotics like quetiapine are used in clinical treatment of major depressive disorder, as well as in forensic toxicology scenarios. The drug–drug interaction (DDI) between quetiapine and duloxetine is worthy of attention to avoid unnecessary adverse effects. However, no pharmacokinetic DDI studies of quetiapine and duloxetine have been reported. In the present study, a rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of quetiapine and duloxetine in rat plasma. A one-step protein precipitation with acetonitrile was applied for sample preparation. The analytes were eluted on an Eclipse XDB-C₁₈ column using the mixture of acetonitrile and 2 mM ammonium formate containing 0.1% formic acid at a gradient elution within 6.0 min. Quantification was performed in multiple-reaction-monitoring mode with the ion transitions m/z 384.4 → 253.2 for quetiapine, m/z 298.1 → 154.1 for duloxetine and m/z 376.2 → 165.2 for IS (haloperidol), respectively. Good linearity was obtained in the range of 0.50–100 ng/mL for quetiapine (r² = 0.9972) and 1.00–200 ng/mL for duloxetine (r² = 0.9982) using 50 μL of rat plasma, respectively. The method was fully validated with accuracy, precision, matrix effects, recovery and stability. The validated data have met the acceptance criteria in FDA guideline. The method was applied to a pharmacokinetic interaction study and the results indicated that quetiapine had significant effect on the enhanced plasma exposure of duloxetine in rats under combination use. This study could be readily applied in therapeutic drug monitoring of major depressive disorder patients receiving such drug combinations.     

Simultaneous determination of amoxicillin and ambroxol in human plasma by LC-MS/MS: validation and application to pharmacokinetic study

A rapid, simple and sensitive LC-MS/MS method was developed for simultaneous determination of amoxicillin and ambroxol in human plasma using clenbuterol as internal standard (IS). The plasma samples were subjected to a simple protein precipitation with methanol. Separation was achieved on a Lichrospher C(18) column (150 mm x 4.6mm ID, dp 5 microm) using methanol (containing 0.2% of formic acid) and water (containing 0.2% of formic acid) as a mobile phase by gradient elution at a flow rate of 1.0 mL/min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 365.9-->348.9 (amoxicillin), m/z 378.9-->263.6 (ambroxol) and m/z 277.0-->203.0 (IS). Calibration curves were linear in the concentration range of 5-20,000 ng/mL for amoxicillin, and 1-200 ng/mL for ambroxol, with the intra- and inter-run precisions of <9% and the accuracies of 100+/-7%. The method has been validated and applied to pharmacokinetic studies of compound amoxicillin and ambroxol hydrochloride tablets in healthy Chinese volunteers.     

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of tenofovir and emtricitabine in human plasma and its application to a bioequivalence study

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for simultaneous quantification of Tenofovir (TEN) and Emtricitabine (EMT) in human plasma using Chromolith Speed Rod RP18. The mass transition ion-pair has been followed as m/z 288.10-->176.10 for TEN, m/z 248.20-->130.20 for EMT and m/z 230.10-->112.10 for Lamivudine (LAM). The method involves solid phase extraction from plasma, simple isocratic chromatographic conditions and mass spectrometric detection using an API 5000 instrument that enables detection at nanogram levels. Lamivudine was used as the internal standard. The proposed method has been validated with a linear range of 10-600 ng/ml for TEN and 25-2,500 ng/ml for EMT. The intrarun and interrun precision values are within 12.0% for TEN and 15.6% for EMT at their respective LOQ levels. The overall recoveries for TEN and EMT were 84.3% and 68.5%, respectively. Total elution time was as low as 2 min.     

Simultaneous determination of lansoprazole and its metabolites 5'-hydroxy lansoprazole and lansoprazole sulphone in human plasma by LC-MS/MS: application to a pharmacokinetic study in healthy volunteers

A highly sensitive and specific liquid chromatography coupled with tandem mass spectrometric (LC-MS/MS) method has been developed and validated for the simultaneous determination of lansoprazole and its metabolites 5'-hydroxy lansoprazole and lansoprazole sulphone. The detection was operated with multiple reaction-monitoring (MRM) using the electrospray ionization technique. The assay procedure involved precipitation of plasma samples with acetonitrile after indapamide was added as internal standard (IS). The chromatographic separation was achieved with a mixture of methanol-0.2% ammonium acetate and 0.1% methanoic acid in water (75:25, v/v) as mobile phase on an Inertsil ODS-3 column. The method was proved to be accurate and precise with linearity ranges of 10-4,000 ng/ml, 5.0-400 ng/ml, and 1.0-400 ng/ml for lansoprazole, 5'-hydroxy lansoprazole and lansoprazole sulphone, respectively, with the correlation coefficients (r) better than 0.999. The lower limits of quantification (LLOQ) were 2.0 ng/ml, 2.0 ng/ml, and 0.5 ng/ml for lansoprazole, 5'-hydroxy lansoprazole and lansoprazole sulphone, respectively. The intra- and inter-day precision and accuracy values were found to be within the assay variability limits (R.S.D.% within +/-15) in accordance with FDA guidelines. The validated LC-MS/MS method has been successfully applied for the determination of lansoprazole and its metabolites in human plasma.     

LC-MS/MS method for simultaneous determination of viramidine and ribavirin levels in monkey red blood cells

A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the simultaneous determinations of total viramidine (viramidine, viramidine monophosphate, viramidine diphosphate, and viramidine triphosphate) and total ribavirin (ribavirin, ribavirin monophosphate, ribavirin diphosphate, and ribavirin triphosphate) in monkey red blood cells (RBC). The method involves the addition of internal standards and perchloric acid, conversion of viramidine or ribavirin phosphorylated metabolites to viramidine or ribavirin, purification with an aminopropyl (NH(2)) solid phase extraction (SPE) cartridge, and LC-MS/MS analysis. The MS/MS is selected to monitor m/z 245-->113, 250-->113, 244-->112, and 249-->112 for ribavirin, [(13)C]ribavirin, viramidine, and [(13)C]viramidine, respectively, using positive electrospray ionization. The calibration curves are linear over a concentration range of 100-10,000 ng/mL (0.412-41.2 microM) with a lower limit of quantification (LLOQ) of 100 ng/mL for both compounds. Mean inter-assay recoveries for ribavirin are 101%, 98.9%, and 96.0%, with coefficient of variance (%CV) values between 1.95 and 4.50% for 100, 1000, and 10,000 ng/mL quality control (QC) samples, respectively. Mean inter-assay recoveries for viramidine are 96.3%, 101%, and 102%, with coefficient of variation (%CV) values between 3.61 and 7.22%, for 100, 1000, and 10,000 ng/mL QC samples, respectively. Over-curve dilution QC at 400 microg/mL (1639 microM) for both viramidine and ribavirin are used to ensure the dilution accuracy (25 X dilutions) for monkey samples. The method has been used to simultaneously determine the total concentrations of ribavirin and viramidine in monkey RBC following 5, 15, and 36 weeks dosing of viramidine or ribavirin (60 mg/kg). The concentrations of total ribavirin following ribavirin dosing are 1242 microM at week 5, 1257 microM at week 15, and 1146 microM at week 36. The concentrations of total ribavirin following viramidine dosing are 634 microM at week 5, 716 microM at week 15, and 683 microM at week 36. Only small amounts of viramidine are detected in RBC following viramidine dosing, 7.80 microM at week 5, 6.63 microM at week 15, and 10.4 microM at week 36. The results suggest that ribavirin levels in RBC were at steady state at week 5 of ribavirin or viramidine dosing. At steady state, ribavirin levels in RBC are approximately 2x after ribavirin dosing than viramidine dosing. The relatively small percentage of viramidine in RBC suggests that viramidine either poorly penetrated into RBC or was extensively converted to ribavirin following entry into RBC.     

液相色谱-串联质谱法测定大鼠血浆中forsklin的浓度及其药代动力学（英文）

目的建立了测定大鼠血浆中forsklin的液相色谱-串联质谱法（LC-MS/MS）。方法血浆样品经叔丁基甲醚萃取后,以水（0.1%甲酸）-乙腈为流动相梯度洗脱,BetaBasic-C18柱分离。通过电喷雾离子化四极杆串联质谱,以多反应监测（MRM）方式进行正离子检测,用于定量分析的离子对分别为m/z 411→375.3（forsklin）和285→193（地西泮）。结果在本实验条件下,forsklin血浆浓度测定方法的线性范围为0.5~1000 ng/ml,定量下限为0.5 ng/ml。日内、日间精密度（相对标准差RSD）均小于14.4%;准确度（相对误差RE）在-3.5%和3.8%之间。方法的专属性,绝对回收率,稳定性和基质效应均符合要求。结论该法快速、灵敏、准确,可用于forsklin的药代动力学研究。     

Development and validation of a LC-MS/MS method with electrospray ionization for determination of LASSBio-579 in rat plasma

A simple and sensitive LC-MS/MS analytical method was developed and validated for the determination of LASSBio-579 in plasma rat, using fluconazole as internal standard. Analyses were performed on a Shimadzu HPLC system using a Shimadzu C18 column and isocratic elution with acetonitrile-water (80:20, v/v), containing 0.4mM ammonium hydroxide and 0.2 mM acetic acid at a flow rate of 1.0 ml/min (split ratio 1:5). A Micromass triple quadrupole mass spectrometer, equipped with an electrospray ionization interface, operated in the positive mode. Plasma samples were deproteinized with acetonitrile (1:2) and 50 microl of the supernatant were injected into the system. The retention times of LASSBio-579 and IS were approximately 4.7 and 2.4 min, respectively. Calibration curves in spiked plasma were linear over the concentration range of 30-2000 ng/ml with determination coefficient >0.98. The lower limit of quantification was 30 ng/ml. The accuracy of method was within 15%. Intra- and inter-day relative standard deviations were less or equal to 13.5% and 6.4%, respectively. The applicability of the LC-MS/MS method for pharmacokinetic studies was tested using plasma samples obtained after intraperitoneal administration of LASSBio-579 to male Wistar rats. No interference from endogenous substances was observed, showing the specificity of the method developed. The reported method can provide the necessary sensitivity, linearity, precision, accuracy, and specificity to allow the determination of LASSBio-579 in pre-clinical pharmacokinetic studies.     

LC-MS/MS法同时测定CUMS大鼠血浆中3种单胺类神经递质

目的建立测定大鼠血浆中五羟色胺(5-HT)、多巴胺(DA)、去甲肾上腺素(NE)的LC-MS/MS方法,观察慢性不可预见性温和应激(chronic unpredictable mild stress,CUMS)抑郁大鼠血浆单胺类神经递质DA、5-HT、NE的变化情况。方法♂SD大鼠22只,分为对照组(n=10)和模型组(n=12),模型组每天给予9种慢性不可预见性温和刺激因子,造模21 d后,分别于造模前后进行行为学测定及眼眶采血;采用苯甲酰氯作为柱前衍生化试剂,将3种待测物及内标衍生化后进入LC-MS/MS检测,测定造模前后血浆中5-HT、NE、DA 3种神经递质浓度。结果造模21d后,与对照组相比,模型组大鼠体重明显降低(P<0.05),水平得分、垂直得分均明显降低(P<0.01),同时糖水消耗量明显降低(P<0.01)。血浆中5-HT、NE、DA的浓度在1.47~752、1.75~898、2.05~1053μg·L-1范围内线性关系良好,最低定量限分别为1.47、1.75、2.05μg·L-1,以质控样品计算,在各浓度水平下,此法的回收率均大于70%,日内和日间精密度小于15%,符合生物样品分析要求。造模21 d后,模型组血浆中5-HT、NE、DA的浓度分别为(3.99±1.21)、(6.24±1.94)、(6.07±1.98)μg·L-1,与对照组相比均明显降低(P<0.01)。结论 CUMS造模成功后,血浆中的3种神经递质分别呈下降趋势。     

LC-MS/MS快速测定人血浆中氯沙坦浓度及其生物等效性研究

目的建立人血浆中氯沙坦LC-MS/MS测定方法,计算氯沙坦人体药动学参数并评价两制剂生物等效性。方法采用单剂量双周期交叉试验设计,完成试验的23例受试者空腹口服受试或参比制剂氯沙坦钾片100 mg后,用甲醇一步沉淀血浆蛋白,并用LC-MS/MS法测定人血浆中氯沙坦浓度。用DAS 3.2.3软件计算氯沙坦人体药动学参数,并评价两制剂生物等效性。结果服用受试和参比制剂后,血浆中氯沙坦的Cmax分别为(697.3±301.7)和(674.1±350.5)ng/m L,AUC0-12 h分别为(994±240)和(1 005±287)ng·h/m L,tmax分别为(1.23±0.38)和(1.37±0.75)h,t1/2分别为(2.04±0.28)和(2.00±0.40)h,生物利用度为102.4%±21.1%。结论建立的分析测试方法灵敏、简便、准确,受试制剂与参比制剂生物等效。     

Oral and i.v. pharmacokinetics of isosteviol in rats as assessed by a new sensitive LC-MS/MS method

A sensitive liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed to investigate isosteviol pharmacokinetics in vivo. Isosteviol was extracted from plasma with hexane and 4% formic acid. A Phenomenex Synergi 2mu Fusion reversed phase analytical HPLC column (50 mm x 2.0 mm) equipped with a Synergi 2micro Fusion guard column was employed for chromatographic separations. The gradient mobile phase consisted of acetonitrile (ACN) and 20mM ammonium acetate at pH 6.5, starting at 20% ACN and ramping to 80% at 7 min, followed by 80% ACN for 1 min, then 20% ACN for 5 min. Negative SRM was used to monitor the m/z 317.1/317.1 and 317.3/317.3 transitions for isosteviol and 395.0/395.0 and 397.0/397.0 transitions for internal standard. The retention time of isosteviol was 9.2 min. The assay was linear over the range of 50-2,000 ng/mL. The accuracy of the method was in the range of 97-105%. Intra- and inter-day precisions were in the range of 1.5-4.6%. Isosteviol (4 mg/kg) was dosed intravenously and orally to Sprague-Dawley rats (n=6). Plasma samples were collected and analysed. Intravenous isosteviol has a distribution half-life of 35.7+/-9.0 min with the initial distribution volume of 68.1+/-9.4 mL. The total clearance, terminal half-life and steady-state volume of distribution were 1.25+/-0.12 mL/min, 150.6+/-50.5 min and 272.6+/-95.9 mL, respectively. The oral bioavailability of isosteviol was found to be 60.4+/-15.5%.     

液相色谱-串联质谱法测定人血浆中阿普唑仑及其代谢物的浓度

目的 建立同时测定人血浆中阿普唑仑(抗焦虑药)及其代谢物α-羟基阿普唑仑、4-羟基阿普唑仑浓度的液相色谱一串联质谱方法.方法 用Asi-lent Zorbax SB C_(18)(2.1 mm×30 mm,3.5μm)色谱柱,流动相为25 mmol·L~(-1)甲酸-乙腈(58:42),流量为0.2 mL·min~-,柱温40℃,进样量50μL,正离子电离、多离子反应监测进行定量分析.结果 阿普唑仑和2个代谢物线性范围分别为0.5～50.0 ng·mL~-(γ=0.9960),0.05～2.00 ng·mL~(-1)(γ=0.9961,0.9922).3者的提取回收率为75.0%～87.3%(RSD<10%).结论 本方法灵敏、准确、快速,可用于临床上阿普唑仑及其代谢产物血药浓度监测和药代动力学研究.     

Development and validation of an improved high-throughput method for the determination of anastrozole in human plasma by LC-MS/MS and atmospheric pressure chemical ionization

In the present study, an automated, 96-well format LC-MS/MS method for the determination of anastrozole in human plasma was developed and fully validated. Within method development procedure, atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) were compared in terms of sensitivity and specificity, with the former proven to be more appropriate and thus being chosen for analyte ionization. In addition, the effect of declustering potential (DP) and collision energy (CE) in sensitivity was, as well, studied and compared between APCI and ESI source employment. Samples were treated with an acetonitrile (ACN) protein precipitation step followed by liquid-liquid extraction (LLE) with methyl t-butyl ether (MTBE) as the organic solvent, using omeprazole as the internal standard (IS). The statistical evaluation for the APCI protocol revealed excellent linearity, accuracy and precision values for the range of concentrations 0.100-100 ng/mL. The method proposed involves the lowest plasma volume so far reported (190 microL), as well as the shortest run time (1.6 min) and along with the employment of two robotic liquid handling systems enabled the rapid and reliable determination of anastrozole in a bioequivalence study (>1000 plasma samples) after per os administration of 1mg tablet within a 4-day period of time.     

液-质联用法测定大鼠血浆中异烟肼及其代谢产物乙酰异烟肼的浓度

目的：建立应用LC-MS/MS测定大鼠血浆中异烟肼及其体内代谢物乙酰异烟肼浓度的方法,并将其应用于异烟肼及乙酰异烟肼在大鼠体内过程的研究。方法：血浆样品采用甲醇沉淀蛋白进行提取,以ESI电离源在正离子模式下检测,用Waters Cortecs C₁₈（4.6 mm×100 mm,2.7 μm）色谱柱,甲醇-水溶液为流动相等度洗脱,流速为0.3 mL·min^-1。结果：异烟肼及乙酰异烟肼在大鼠血浆中的线性范围及定量限均符合测定要求,日内、日间精密度及基质效应均<15%。结论：本方法快速、灵敏、专属性强且重现性好,可用于大鼠血浆中异烟肼及乙酰异烟肼药动学研究。     

Liquid chromatographic-tandem mass spectrometric method for the simultaneous quantitation of telmisartan and hydrochlorothiazide in human plasma

A rapid and sensitive method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the simultaneous determination of telmisartan and hydrochlorothiazide in human plasma. Sample preparation involved liquid-liquid extraction with diethyl ether-dichloromethane (60:40, v/v). The analytes and internal standard, probenecid, were separated on a Venusil XBP-C(8) column using gradient elution with acetonitrile-10 mM ammonium acetate-formic acid at a flow rate of 1.2 mL/min. Detection was by electrospray negative ionization mass spectrometry using multiple reaction monitoring of the transitions at m/z 513.0-->469.4 for telmisartan, m/z 295.9-->268.9 for hydrochlorothiazide and m/z 283.9-->239.9 for probenecid. For both analytes, the method was linear in the range 1.00-600 ng/mL with intra- and inter-day precision (as relative standard deviation) 相似文献   

LC-MS/MS同时测定大鼠血浆中的托莫西汀与牛磺酸及其药动学研究

目的 采用LC-MS/MS法同时测定大鼠血浆中的托莫西汀与牛磺酸,比较托莫西汀单独给药与托莫西汀联合牛磺酸给药两种方式下托莫西汀的药动学参数.方法 色谱柱为Inertsil ODS-3(100 mm×2.1 mm,5μm),流动相为含0.2％甲酸的甲醇-20 mmol·L-1乙酸铵的水溶液(80∶20),流速0.3 mL· min-1;质谱采用电喷雾接口,正离子模式,多反应监测.结果 托莫西汀和牛磺酸的线性范围分别为0.935～935 ng· mL-1和0.564～112.8 μg·mL-1(r2 ＞0.99),最低定量限分别为0.935ng· mL-1、0.564 μg· mL-1;方法 的日内和日间精密度均＜5.25％;稳定性试验证明牛磺酸和托莫西汀比较稳定.结论 所用方法灵敏度高,选择性好,分析速度快,可用于同时测定血浆中托莫西汀与牛磺酸的含量;在牛磺酸辅助托莫西汀用于治疗注意力缺陷障碍时,托莫西汀的药动学参数与单用托莫西汀时的相比无显著性差异.     

Simultaneous determination of ciclesonide and its active metabolite desisobutyryl-ciclesonide in human plasma by LC-APCI-MS/MS: application to pharmacokinetic study in healthy Chinese volunteers

A sensitive and highly selective liquid chromatography tandem mass spectrometric (LC/MS/MS) method was developed and validated for the determination of ciclesonide (CIC) and its active metabolite, desisobutyryl-ciclesonide (des-CIC), in human plasma. Plasma samples were extracted using methyl tert-butyl ether with mifepristone as an internal standard (IS). Separation was carried out on a C(18) column using a mixture of 0.1% formic acid solution and methanol as the mobile phase with linear gradient elution. The detection was operated with positive atmospheric pressure chemical ionization (APCI) by selective multiple reaction monitoring (SRM). The chief benefit of the present method was the high sensitivity, with the lower limit of quantification (LLOQ) as low as 10pg/mL and the linearity ranging from 10 to 10,000pg/mL for both CIC and des-CIC. The method was fully validated and successfully applied to determine CIC and des-CIC simultaneously in human plasma and proved to be suitable for phase I clinical pharmacokinetic study of inhaled ciclesonide in healthy Chinese volunteers.     

LC-MS/MS method for the determination of carbamathione in human plasma

Liquid chromatography-tandem mass spectrometry methodology is described for the determination of S-(N,N-diethylcarbamoyl)glutathione (carbamathione) in human plasma samples. Sample preparation consisted of a straightforward perchloric acid medicated protein precipitation, with the resulting supernatant containing the carbamathione (recovery ~98%). For optimized chromatography/mass spec detection a carbamathione analog, S-(N,N-di-i-propylcarbamoyl)glutathione, was synthesized and used as the internal standard. Carbamathione was found to be stable over the pH 1-8 region over the timeframe necessary for the various operations of the analytical method. Separation was accomplished via reversed-phase gradient elution chromatography with analyte elution and re-equilibration accomplished within 8 min. Calibration was established and validated over the concentration range of 0.5-50 nM, which is adequate to support clinical investigations. Intra- and inter-day accuracy and precision determined and found to be <4% and <10%, respectively. The methodology was utilized to demonstrate the carbamathione plasma-time profile of a human volunteer dosed with disulfiram (250 mg/d). Interestingly, an unknown but apparently related metabolite was observed with each human plasma sample analyzed.