Aim:To develop a rapid high-performance liquid chromatography-mass spectrometry (HPLC-MS) method for the quantification of tiopronin in human plasma.Methods:Cysteine was chosen as antioxidant and firstly added into the whole blood firstly.After adding mycophenolic acid as internal standard (IS) and 1 mol/L HCl into the plasma,the samples were extracted with acetic ether and then determined by HPLC-MS.The chromatographic separation was performed on a Shim-pack VP-ODS C18 column (250 mm×2.0 mm,5 μm) using methanol-0.1% acetic acid (70∶30) as mobile phase with a flow rate of 0.2 mL/min.Results:The assay exhibited a linear range of tiopronin between 30～4 000 ng/mL.The precisions for intra- and inter-batch were all within 8.5%.The extraction recoveries were more than 70%.The total HPLC-MS analysis time was within 7.5 min per a run.The fully validated method was successfully applied to quantify tiopronin in human plasma for a bioavailability study.Conclusion:The assay proved to be accurate,sensitive,selective and convenient.The fully validated method can be applied to study the pharmacokinetics and bioavailability of tiopronin and tiopronin formulations in human.

A rapid and simple high performance liquid chromatographic method coupled with tandem mass spectrometry (LC–MS–MS) via electrospray ionization (ESI) has been developed and validated to separate and simultaneously quantify sodium ferulate (SF), salicylic acid (SA), cinnarizine (CIN) and vitamin B1 (VB1) in human plasma. Gemfibrozil (GEM) was used as the internal standard (IS) for SF and SA, whereas lomerizine (LOM) was used as the IS for CIN and VB1. The plasma samples were prepared by one-step protein precipitation followed by an isocratic elution with 10 mM ammonium acetate buffer (pH = 5.0): acetonitrile (35:65, v/v,) on an Agilent Zorbax SB-CN column (150 mm × 2.0 mm ID, 5 μm). The precursor and product ions of these drugs were monitored on a triple quadrupole mass spectrometer, operating in the selected reaction monitoring mode (SRM) with polarity switch, in the negative-ion mode for SF, SA and GEM, in the positive-ion mode for CIN, VB1 and LOM. The method was validated over the concentration range of 1.5–1,000 ng mL−1 for SF, 20–5,000 ng mL−1 for SA, 2–500 ng mL−1 for CIN, 1–30 ng mL−1 for VB1. The intra- and inter-batch precisions were less than 15% of the relative standard deviation. The recoveries for analytes and IS achieved from spiked plasma samples were consistent and reproducible. The validated LC–MS–MS method has been successfully applied to the pharmacokinetic study of sodium ferulate and aspirin capsule in healthy volunteers.