Simultaneous determination and pharmacokinetic study of metformin and rosiglitazone in human plasma by HPLC-ESI-MS

A fast, sensitive and specific high-performance liquid chromatography tandem mass spectrometry method was developed for simultaneous determination of metformin and rosiglitazone in human plasma. With phenformin as an internal standard, the analysis was carried out on a C(18) column (50 mm × 2.1 mm, 3.5 μm) using a mobile phase consisting of acetonitrile-10 mM ammonium acetate (20:80, v/v). The detection was performed by tandem mass spectrometry via electrospray ionization. Linear calibration curves were obtained in the concentration of 1.054-263.5 ng/mL for rosiglitazone and 4.040-5050 ng/mL for metformin. The method was applicable to clinical pharmacokinetic study of metformin and rosiglitazone in healthy volunteers following oral administration.     

液相色谱-串联质谱法测定虾夷扇贝和长牡蛎中软骨藻酸的残留

建立了液相色谱-串联质谱测定虾夷扇贝和长牡蛎中贝类毒素软骨藻酸残留的检测方法。样品经50%甲醇提取,LC-SAX柱净化,3mL0.1mol/L甲酸溶液洗脱,电喷雾离子源(ESI),在正离子、多反应监测方式(MRM)模式下进行定性与定量,定性离子对为m/z 311.98/265.91,m/z 311.98/247.9,m/z 311.98/192.91,以m/z 311.98/265.91为定量离子对,外标法定量。结果表明,方法的检测限为0.01μg/g,定量限为0.02μg/g。在0.02~10μg/mL范围内线性相关系数为0.9999。当添加软骨藻酸质量分数为20~1000 ng/g时,虾夷扇贝样品中软骨藻酸的平均回收率为81.3%~105.4%,RSD为3.9%~8.9%(n=6);长牡蛎样品中软骨藻酸的平均回收率为83.5%~106.6%,RSD为4.6%~6.4%(n=6)。方法满足对贝类产品中软骨藻酸残留的测定。     

Determination of glycyrrhizin in dog plasma by liquid chromatography-mass spectrometry and its application in pharmacokinetic studies

A sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method was established and validated for the determination of glycyrrhizin in dog plasma. After treatment with methanol to precipitate proteins, plasma samples were analyzed on a reversed-phase C18 (ODS) column with a mobile phase of methanol:1% formic acid solution (75:25, v/v). MS determination was performed using negative electrospray ionization (negative ESI) in the selected ion monitoring mode. Glycyrrhizin was monitored at the m/z 821 channel and internal standard (gliquidone) at the m/z 526 channel. The calibration curve was linear over the range from 0.05 μg mL(-1) to 10 μg mL(-1) with a correlation coefficient above 0.99. This method was successfully applied to the pharmacokinetic studies in beagle dogs. The absolute bioavailability of glycyrrhizin in beagle dogs was 3.24%.     

QuEChERS-超高效液相色谱-串联质谱法检测羊肉中8种抗真菌药

建立了QuEChERS-超高效液相色谱-串联质谱（UPLC-MS/MS）检测羊肉中8种抗真菌药的方法。羊肉样品用含2.0%（体积分数）甲酸的乙腈溶液提取后,采用QuEChERS方法净化。采用Atiantis^® T3色谱柱（100 mm×2.1 mm,3 μm）进行分离,以乙腈-0.1%（v/v）甲酸水溶液为流动相进行梯度洗脱,在电喷雾电离源、正离子模式（ESI⁺）和多反应监测模式（MRM）下进行定性定量分析。实验比较了不同提取溶剂的提取效果,并优化了色谱和质谱的分析条件。结果表明,8种抗真菌药物在0.2~50 μg/L范围内线性关系良好,相关系数（R²）均>0.99;检出限（LOD）为0.3~3.0 μg/kg,定量限（LOQ）为1.0~10.0 μg/kg。8种抗真菌药在低、中、高3个水平下的平均加标回收率为70.3%~118.4%,相对标准偏差（RSD）为0.4%~4.3%（n=6）。该方法灵敏高效,回收率优良,重复性好,适用于羊肉样品抗真菌药物的有效检测。     

Profiling histidine-containing dipeptides in rat tissues by liquid chromatography/electrospray ionization tandem mass spectrometry

The histidine-containing dipeptides carnosine (CAR) and structurally related anserine (ANS) and homocarnosine (HCAR), widely distributed in vertebrate organisms, have recently been proposed as endogenous quenchers for highly cytotoxic alpha,beta-unsaturated aldehydes generated by peroxidation. A sensitive, selective, specific and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric assay was developed and validated for the simultaneous determination of these peptides in biological matrices in order to establish their plasma/tissue distribution. Samples (plasma or tissue homogenates from male rats) were prepared by protein precipitation with HClO(4) (1 : 1, v/v) containing H-Tyr-His-OH as internal standard. The supernatant was separated on a Phenomenex Sinergy polar-RP column with a mobile phase of water-acetonitrile-heptafluorobutyric acid (9 : 1 : 0.01, v/v/v) at a flow-rate of 0.2 ml min(-1), with a run time of 10 min. Detection was effected on an ion trap mass spectrometer equipped with an electrospray ionization interface operating in positive ionization mode. The acquisitions were in the multiple reaction monitoring mode using the following precursor --> product ion combinations: H-Tyr-His-OH (internal standard) m/z 319 --> 301; CAR m/z 227 --> 210 + 209; ANS m/z 241 --> 224 + 197 + 170; HCAR m/z 241 --> 156. The method was validated over the concentration range 15-1000 nmol g(-1) and the limit of quantification (LOQ) and limit of detection (LOD) were 12.5 and 4.2 pmol injected, respectively. The intra- and inter-day precisions were <10% (< or =17.47% at the LOQ) and the intra- and inter-assay accuracies were within +/-10% for all concentrations. The mapping profile in rat tissue gave the following results: the highest concentrations of CAR and ANS were found in skeletal muscles (soleus, gastrocnemius, tibialis), followed by the heart, cerebellum and brain (ANS below the LOQ). HCAR was found only in the brain and cerebellum. No histidine-containing dipeptides were detectable in plasma, liver, kidney and lung.     

Rapid and specific approach for direct measurement of glimepiride in human plasma by LC-ESI-MS-MS employing automated 96 well format: application to a bioequivalence study

A rapid liquid chromatographic method with electrospray ionization tandem mass spectrometric (LC-MS-MS) detection is developed and validated for quantification of glimepiride in heparinized human plasma. Plasma samples, without a drying and reconstitution step, are extracted by solid-phase extraction (SPE) and eluted with 0.9 mL of acetonitrile-methanol (1:1, v/v) containing 0.05% formic acid. The analyte and glimepiride d8 (internal standard, IS) are chromatographed on a C(18) column; the mobile phase is acetonitrile-2 mm ammonium formate (88:12, v/v), with the pH adjusted to 3.5 with formic acid, at a flow rate of 0.5 mL/min. The retention times of glimepiride and the IS are 0.93 min, and the runtime is 1.6 min per sample. Selected reaction monitoring of MH(+) at m/z 491.20 and 499.26 result in stable fragment ions with m/z 351.80 and 359.96 for glimepiride and the IS, respectively. The response was a linear function of the concentration in the range of 2.0-650.0 ng/mL, with r ≥ 0.9994. The recovery of glimepiride and the IS ranged from 81.91 to 83.36%. The assay has excellent characteristics and has been successfully used for the analysis of glimepiride in healthy human subjects in a bioequivalence study. It was well suited to clinical studies of the drug involving large numbers of samples.     

超高效液相色谱-串联质谱法测定兔血浆中的丝裂霉素C

建立了采用超高效液相色谱-串联质谱测定兔血浆中丝裂霉素C的方法。以兔空白血浆为基质,通过添加标准溶液的方法配制含丝裂霉素C和内标物曲安奈德的样品,选用乙酸乙酯为提取溶剂,液-液萃取法处理血浆样品。采用Hypersil Gold C18分析柱(50 mm×2.1 mm, 1.9 μm),流动相为甲醇-0.1%甲酸水溶液(90:10, v/v),等度洗脱,流速0.2 mL/min,柱温35 ℃,在3 min内实现了快速分离。采用电喷雾正离子(ESI+)模式电离,选择反应监测(SRM)模式检测,以曲安奈德作为内标物进行定量。用于监测的定量离子对分别为丝裂霉素C m/z 335.2→242.2和曲安奈德m/z 435.2→397.3/415.2,用基质匹配标准溶液法进行定量。结果表明: 兔血浆中丝裂霉素C的质量浓度在1～1000 μg/L范围内线性关系良好(r=0.9978,权重系数(weighting): 1/x2);血浆中丝裂霉素C的检出限(信噪比为3)为0.2 μg/L;其平均回收率为85%～ 115%;日内及日间的相对标准偏差(RSDs)均小于15%,满足生物样品检测的要求。该方法可用于兔气管外壁给药后的血浆样品中丝裂霉素C的检测。本方法选择性强、灵敏度高、操作简便快速、重现性好,适用于丝裂霉素C药代动力学等方面的研究。     

超高效液相色谱-串联质谱法测定食用植物油中胆固醇含量

提出了食用植物油中胆固醇的超高效液相色谱-串联质谱测定方法。食用植物油经皂化后用石油醚-乙醚(1+1)溶液提取,以Waters ACQUITY UPLC BEH C18色谱柱(50mm×2.1mm,5μm)为分离柱,以甲酸-甲醇(0.1+99.9)溶液为流动相,以2,2,3,4,4,6-d6胆固醇为内标,采用大气压化学电离源在多反应监测负离子模式下进行测定,胆固醇和内标的定量离子对分别为m/z369.2/146.9,369.2/160.9和375.2/166.5。胆固醇在0.1～5mg·L-1范围内呈线性,测定下限(10S/N)为0.02ng。在3个浓度水平上对方法做回收试验,测得回收率在102%～110%之间。     

高效液相色谱-质谱联用测定胶原蛋白中的羟脯氨酸

建立了一种简单、快速地测定胶原蛋白中羟脯氨酸(HYP)的高效液相色谱-电喷雾质谱(HPLC-ESI/MS)方法。胶原蛋白经酸水解后,以乙腈-0.05%的三氟乙酸水溶液(体积比为5∶95)为流动相,以1.0 mL/min的流速在C8反相柱上进行分离。以茶氨酸为内标,利用质谱定性定量测定HYP。在电喷雾正离子模式下,对m/z 132和m/z 175离子进行选择离子监测。在11.7～117 mg/L范围内,HYP与内标物茶氨酸的峰面积比和HYP的质量浓度呈良好的线性关系,相关系数为0.9993。含量测定的相对标准偏差为1.87%,回收率为97.85%～101.76%。此方法流动相简单,分析时间短且无需衍生处理,抗干扰能力强,能准确快速地测定胶原蛋白中HYP的含量。     

酸化沉淀蛋白-超快速液相色谱-串联质谱法测定肝损伤大鼠血浆中的头孢呋辛

为了研究二代头孢类新药头孢呋辛赖氨酸在肝损伤大鼠体内的药代动力学过程,建立了采用超快速液相色谱-串联质谱(UFLC-MS/MS)快速测定肝损伤模型大鼠血浆中头孢呋辛含量的方法。血浆样品在酸性条件下用乙腈沉淀蛋白,采用Shim-pack XR-ODS色谱柱(75 mm×3.0 mm, 2.2 μm)为分析柱、乙腈-0.1%甲酸水溶液(40:60, v/v)为流动相、流速为400 μL/min进行色谱分离,采用电喷雾负离子(ESI~)模式电离、多反应监测(MRM)模式进行质谱检测,用于定量分析的离子对分别为m/z 423.2→206.8 (头孢呋辛)和m/z 454.1→238.4 (内标头孢噻肟)。结果表明,大鼠血浆中头孢呋辛的质量浓度在0.01～1 mg/L和1～400 mg/L范围内线性关系良好(r＞0.99),定量限为0.01 mg/L,日内和日间精密度(以相对标准偏差(RSD)计)均小于11.5%,准确度(RE)为~7.1%～2.2%,平均萃取回收率大于83.5%,样品运行时间仅为3.0 min,能够满足生物样品的测定需求。该法简便、快速,已用于肝损伤大鼠静脉注射头孢呋辛赖氨酸的药代动力学预实验研究。     

Delapril and manidipine measurements by liquid chromatography-tandem mass spectrometry in a pharmaceutical formulation

A simple, specific, fast and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous analysis of delapril (DEL) and manidipine (MAN) from their combination formulation was developed and validated using fesoterodine as the internal standard (IS). The LC-MS/MS method was carried out on a Luna C8 column (50 × 3.0 mm i.d., 3 μm) with a mobile phase consisting of methanol and 10 mmol L(-1) ammonium acetate (90 : 0, v/v), run at a flow rate of 0.25 mL min(-1). The mass spectrometry method was performed employing positive electrospray ionization operating in multiple reaction monitoring mode, monitoring the transitions of m/z 453.1 → 234.1 for DEL, m/z 611.1 → 167.0 for MAN and m/z 412.2 → 223.0 for IS. The total analysis time was 3 min and the method was linear in the concentration range of 6-1080 ng mL(-1) and 2-360 ng mL(-1) for DEL and MAN, respectively. Parameters investigated for the method validation, such as the specificity, linearity, precision, accuracy and robustness, gave results within the acceptable range. Moreover, the proposed method was successfully applied for the simultaneous determination of DEL and MAN and the results were compared to validated liquid chromatography and capillary electrophoresis methods showing non-significant differences (P = 0.9).     

Capillary zone electrophoresis/mass spectrometry of 5-aminolaevulinic acid and porphobilinogen

A capillary zone electrophoresis/electrospray ionisation mass spectrometry (CZE/ESI-MS) method has been developed for the separation and detection of 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG). Capillaries were 70 cm long with an inner diameter of 75 micrometer and outer diameter of 375 micrometer. The buffer used was aqueous ammonium acetate (50mM, pH 5.2) with a co-axial 'make-up' flow of methanol/aqueous 0.1% formic acid (1:1 v/v) at a flowrate of 6 microL/min. A voltage of 20 kV was used for CZE and an ESI voltage of 3.5 kV. Full scan data was acquired over the range m/z 100-500 in positive ion mode, from which selected ion electropherograms were extracted; at m/z 132 for the protonated molecular ion of ALA and m/z 210 for the methylenepyrrolenine fragment ion of PBG. The protonated molecular ion of PBG, m/z 227, was found to be too facile to monitor, easily losing ammonia in the electrospray source and better sensitivity was achieved by monitoring the resulting fragment ion. The detection limits were circa 100 attomoles of ALA and 10 attomoles of PBG at a signal-to-noise ratio (S/N) better than 10, providing sufficient sensitivity for clinical use and offering advantages over existing techniques.     

超高效液相色谱-串联质谱法测定人血浆中盐酸氨溴索及其制剂的生物等效性评价

采用超高效液相色谱-串联质谱（UHPLC-MS/MS）技术,建立了快速、简单、灵敏的测定人血浆中盐酸氨溴索含量的方法,并用于盐酸氨溴索人体生物等效性预试验研究。取50 μL血浆样品,采用蛋白沉淀法处理,以盐酸氨溴索-d5为内标。采用Waters XBridge BEH C18色谱柱（50 mm×2.1 mm,2.5 μm）,以0.1%（v/v）甲酸水-含0.1%（v/v）甲酸的甲醇为流动相,在0.4 mL/min流速下进行梯度洗脱。采用电喷雾电离（ESI）源以正离子模式进行MRM检测。结果显示,盐酸氨溴索在2~400 ng/mL范围内线性关系良好,相关系数（r）为0.998,准确度为97.1%~108.7%,精密度为1.0%~5.6%。将该方法用于6名健康受试者口服盐酸氨溴索受试制剂和参比制剂30 mg后血药浓度的测定,结果显示二者相对生物利用度为（102.3±14.8）%,血药浓度-时间曲线下面积（AUC_0-t、AUC_0-∞）和最大血药浓度（C_max）的90%置信区间均在80.0%~125.0%范围内,两种制剂生物等效。     

Determination of glycoalkaloids and relative aglycones by nonaqueous capillary electrophoresis coupled with electrospray ionization-ion trap mass spectrometry

Glycoalkaloids are naturally occurring nitrogen-containing compounds present in many species of the family Solanaceae, including cultivated and wild potatoes (Solanum spp.), tomatoes (Lycopersicon spp.), etc. These compounds have pharmacological and toxicological effects on humans due to their significant anticholinesterase activity and disruption of cell membranes. Herein is reported the development of a capillary electrophoresis (CE) method using nonaqueous (NA) separation solutions in combination with ion trap mass spectrometry (MS and MS/MS) detection for the identification and quantification of glycoalkaloids and their relative aglycones. A mixture 90:10 v/v of MeCN-MeOH containing 50 mM ammonium acetate and 1.2 M acetic acid (applied voltage of 25.5 kV) was selected as a good compromise for the separation and detection of these compounds. The electrospray MS measurements were carried out in the positive ionization mode using a coaxial sheath liquid, methanol-water (1:1) with 1% of acetic acid at a flow rate of 2.5 microL/min. Under optimized experimental conditions, the predominant ion was the protonated molecular ion ([M+H](+)) of solanidine (m/z = 398), tomatidine (m/z = 416), chaconine (m/z = 852), solanine (m/z = 868), and tomatine (m/z = 1034). MS/MS experiments were carried out systematically by changing the relative collisional energy and monitoring the intensities of the fragment ions that were not high enough to allow better quantification than with the mother ions. The method was used for analyzing glycoalkaloids in potato extracts.     

A novel bioanalytical method based on UHPLC‐HRMS/MS for the quantification of oleuropein in human serum. Application to a pharmacokinetic study

A highly sensitive, rapid and specific ultrahigh‐performance liquid chromatography, coupled to negative electrospray ionization high‐resolution tandem mass spectrometry, method was developed and validated in order to investigate the absorption of dietary oleuropein (OE) in human subjects. Serum samples were collected at predefined time points, after oral administration of an olive leaf extract enriched in OE (204.4 mg OE per capsule) to two subjects. Subsequently, samples were analyzed by the developed method after a simple solid‐phase extraction step. Chromatographic separation was operated with aqueous formic acid, 0.1% (v/v), and acetonitrile following a gradient program at a flow rate of 0.45 mL/min in an RP‐C₁₈ (50 × 2.1 mm, 1.9 μm) column with a total run time of 2.7 min. The method was validated and successfully applied to the determination of OE in human serum, with the pharmacokinetic analysis of the data revealing a biphasic response.     

高效液相色谱-串联质谱法同时测定贝类中22种农药残留

建立了高效液相色谱-三重四极杆质谱（HPLC-MS/MS）同时测定贝类中22种农药残留的分析方法。样品经含0.1%（v/v）甲酸的乙腈提取，N-丙基乙二胺（PSA）和石墨化碳黑（GCB）净化，然后采用ACE UltraCore 2.5 SuperC18柱（100 mm×2.1 mm，2.5 μm）分离，以甲醇-0.1%（v/v）甲酸水溶液为流动相梯度洗脱，流速为0.4 mL/min，柱温为35 ℃，然后以电喷雾电离（ESI）源，在多反应监测（MRM）、正离子模式下，采用三重四极杆质谱检测。22种农药在各自的线性范围内线性关系良好，相关系数均大于0.997，检出限为0.1~0.3 μg/kg，定量限为0.3~1.0 μg/kg。在3个添加水平下，22种农药的平均回收率为65.2%~109.4%，相对标准偏差为1.3%~15.2%（n=6）。该方法操作简单，快速，准确度高，灵敏度高，可用于贝类中22种农药残留的同时检测。     

A validated liquid chromatographic/tandem mass spectrometric method for the determination of phencyclidine in microliter samples of rat serum

A liquid chromatographic/tandem mass spectrometric method is described for the determination of phencyclidine (PCP) in small volumes of rat serum (e.g. 50 microl). Samples were extracted using a mixed-mode strong cation-exchange column and then separated isocratically using a narrow-bore (2.1 mm i.d.) 3 microm Hypersil phenyl column and a mobile phase consisting of an ammonium formate buffer (pH 2.7) with 60% (v/v) methanol. Detection was accomplished using positive ion electrospray ionization in the multiple reaction monitoring mode. Mass spectra were obtained and peaks were observed at an m/z (% abundance) of 244 (100), 159 (25), and 86 (89). Tandem mass spectra were also obtained from the m/z 244 precursor ion with peaks observed at m/z 159 (100), 86 (96), and 91 (11). Optimum serum PCP sensitivity and precision were obtained at a transition of m/z 244 --> 159. Matrix-associated ion suppression did not significantly affect the accuracy (100-112%) or precision (CV < or =8%) of the assay. The lower limit of quantitation was 1 ng ml(-1) in 50 microl of serum. The method was used to study the serum pharmacokinetics of PCP in rats after an intravenous bolus dose of PCP.     

Fast and sensitive LC-DAD-ESI/MS method for analysis of saikosaponins c, a, and d from the roots of Bupleurum Falcatum (Sandaochaihu)

In the present study, we developed a liquid chromatography-diode array detector-electrospray ionization/mass spectrometric (LC-DAD-ESI/MS) method for analysis of saikosaponins in Bupleurum falcatum. The LC method employed a ZORBAX SB-Aq analytical column (150 x 4.6 mm i.d., 5 μm) at a flow rate of 0.8 mL/min coupled with a diode array detector at 204 nm. A step gradient of acetonitrile-water (v/v) containing 0.5% formic acid from 30 to 70% was applied, leading to a sample analysis time of 30 min. The ESI-MS was carried out in positive and negative modes from 500 to 1,500 m/z. Saikosaponins c, a, and d gave strong sodium adducts at m/z 949.6, 803.5 and 803.6, respectively, in positive mode. The data indicate that the present LC-DAD-ESI/MS assay is an effective method for the determination of saikosaponins c, a and d from the roots of Bupleurum falcatum.     

高效液相色谱-串联质谱法同时测定废水中18种酚类污染物

建立了上清液直接进样-高效液相色谱-串联质谱同时测定废水中18种酚类污染物的分析方法。取5.0 mL水样置于具塞离心管中,加氨水调节pH≥12,摇匀,加入1.0 mL二氯甲烷-正己烷(2: 1, v/v)混合溶液并振摇5 min, 4000 r/min离心5 min,用玻璃针筒抽取上清液并经0.22 μ m聚四氟乙烯滤膜过滤,用甲酸调节水样pH至中性;然后采用Thermo Hypersil ODS柱(100 mm×2.1 mm, 5.0 μ m)分离,以甲醇-0.01 mol/L甲酸铵-甲酸水溶液(pH 4.0)为流动相进行梯度洗脱,流速0.2 mL/min,柱温30℃,进样10 μ L,电喷雾负离子电离(ESI^-)模式、多反应监测(MRM)模式进行检测,外标法定量。18种酚类化合物的峰面积与其质量浓度在一定浓度范围内均呈良好的线性关系(r²≥0.9991),方法检出限为0.10~0.88 μ g/L。测定低、中、高加标浓度的样品,18种酚类化合物的相对标准偏差为2.5%~9.9%(n=6);火工药剂废水与石油化工废水样品中的平均加标回收率为68.7%~118%(n=3)。此方法操作简单,灵敏度高,干扰小,分析速度快,可适用于环境废水中18种酚类污染物的同时分析。     

Simultaneous determination of amiloride and hydrochlorothiazide in human plasma by liquid chromatography/tandem mass spectrometry with positive/negative ion-switching electrospray ionisation

A new method for simultaneous determination of amiloride and hydrochlorothiazide by liquid chromatography/electrospray tandem mass spectrometry (LC/MS/MS) operated in positive and negative ionization switching mode was developed and validated. Protein precipitation with acetonitrile was selected for sample preparation. The analytes were separated on a Phenomenex Curosil-PFP (250x4.6 mm, 5 microm) column by a gradient elution with a mobile phase consisting of 0.15% formic acid solution containing 0.23% ammonium acetate and methanol pumped at a flow rate of 1.0 mL.min(-1). Rizatriptan was used as the internal standard (IS) for quantification. The determination was carried out on a Waters Quattro-micro triple-quadrupole mass spectrometer operated in multiple reaction monitoring (MRM) mode using the following transitions monitored simultaneously: positive m/z 230-->171 for amiloride, m/z 270-->158 for rizatriptan, and negative m/z 296-->205 for hydrochlorothiazide. The lower limits of quantification (LLOQs) were 0.1 and 1.0 ng.mL(-1) for amiloride and hydrochlorothiazide, respectively, which were lower than other published methods by using ultraviolet (UV), fluorimetric or mass spectrometric detection. The intra- and inter-day precision and accuracy were studied at three different concentration levels and were always better than 15% (n=5). This simple and robust LC/MS/MS method was successfully applied to the pharmacokinetic study of compound amiloride and hydrochlorothiazide tablets in healthy male Chinese volunteers.