Sensitive and specific method for the determination of josamycin in human plasma by liquid chromatography-mass spectrometry

A highly sensitive and specific method for the determination of josamycin in human plasma by LC-MS was developed and validated. Josamycin was extracted from human plasma by a single-step liquid-liquid extraction and analyzed by LC-MS via an electrospray ionization interface. Selected ion monitoring was used to detect josamycin and its internal standard. The intra-day precision and accuracy, expressed as C.V. and R.E., ranged from 2.8% to 13.5% and -10.3% to 7.6%, respectively. The lower limit of detection was 0.1 ng/ml and the lower limit of quantitation was set at 1 ng/ml when 0.5 ml of plasma was used. No endogenous interference was observed in human plasma obtained from drug-free volunteers.