A sensitive liquid chromatography–electrospray ionization-mass spectrometry (LC–ESI-MS) method for determination of eperisone

spectrometry (LC–ESI-MS) method for determination of eperisone in human plasma using buflomedil as the internal standard (IS) is established. After being made alkaline with saturated sodium bicarbonate solution, plasma samples are extracted with a mixture of diethyl ether–cyclohexane (1:1, v/v) and separated by highperformance liquid chromatography on a reversed-phase C1 8 column with a mobile phase of 10mM ammonium acetate buff e r (adjusted the pH to 3.9 with acetic acid)–methanol (20:80, v/v). Eperisone is determined using ESI in a single-quadrupole MS. LC–ESI-MS is performed in the selected ion monitoring mode using target ions at m / z 260 for eperisone and m / z 308 for the IS. Calibration curves are linear over the ranges 0.02–20 ng/mL for eperisone. The intraand interassay variability values are less than 9.0% and 11.5%, respectively. The mean plasma extraction recovery of eperisone is 91.7 ± 6.6%. The method has been successfully applied to study the pharmacokinetics of eperisone in h e a l t h y, male, Chinese volunteers. Pharmacokinetic parameters of the reference and test tablets have been compared.