RESUMO
OBJECTIVE: To establish an LC-MS/MS method for the determination of isoniazid and moxifloxacin in human plasma and pleural effusion. METHODS: The theophylline was used as internal. The protein of samples were precipitated with acetonitrile. The supernatant was separated on an Agilent ZORBAX SB-Aq (4.6 mm×150 mm, 5 μm). The mobile phase was consisted of acetonitrile and 5 mmol·L-1 ammonium acetate(0.1% formic acid solution). Electrospray ionization (ESI) source was applied and operated in the positive multiple reaction monitoring (MRM) mode. The MS/MS ion transition of m/z was 138.1/121.1 for isoniazid, 402.1→384.0 for moxifloxacin and 181.1/124.0 for theophylline. RESULTS: Chromatograms showed no endogenous interfering peaks with blank samples.The calibration curves of isoniazid and moxifloxacin were both linear over the concentration range of 0.1-10 μg·mL-1. Both inter-and intra-day relative standard deviations were less than 7.56%. CONCLUSION: The method is specific, sensitive and accurate, and proved to be suitable for the determination of isoniazid and moxifloxacin in human plasma and pleural effusion samples.