Abstract: Objective To establish a liquid chromatography-mass spectrometry (LC-MS/MS) method for simultaneous determination of acetaminophen (APAP) and its toxicity related metabolite acetaminophen-cysteine (APC) in mouse plasma. Methods Theophylline was taken as the internal standard (IS) while plasma samples were pretreated by volatilizing and re-dissolving the supernatant after protein precipitation. The gradient was eluted by Agilnet Zorbax SB-C₁₈ (3.0 mm×100 mm, 3.5 μm). The aqueous phase was an aqueous solution containing 0.1% formic acid while the organic phase was a methanol solution containing 0.1% formic acid. The contents of APAP and APC were detected under positive ions detection with electrospray ionization (ESI) in the selective ion monitoring (SRM) mode of m/z 152.1→110.0 and 271.0→140.0 in the triple quagdrupole tandem mass spectrometer (TSQ Quantum Ultra). Results There were good linear relationships when concentrations ranged from 60 ng·mL^-1 to 3 000 ng·mL^-1 for APAP and from 20 ng·mL^-1 to 1 000 ng·mL^-1 for APC. The selectivity, accuracy and precision, matrix effect and extraction recovery of the method met the requirements of biological sample analysis. Conclusion The LC-MS / MS method established in this study could be applied to the pharmacokinetics of APAP and APC in mice.

Key words: acetaminophen, acetaminophen-cysteine, N-acetylcysteine, LC-MS/MS, pharmacokinetics, mouse, toxicity