LC/MS/MS measurement of penicillin G in bovine plasma, urine, and biopsy samples taken from kidneys of standing animals.

Methods for the measurement of penicillin concentration in bovine plasma, kidney and urine were developed and validated. Detection was based on liquid chromatography/tandem mass spectrometry (LC/MS/MS). Phenethecillin was used as an internal standard. Plasma was extracted with acetonitrile using a method with a calculated limit of quantitation (LOQ) of 12 ng/mL. Kidney samples were homogenized in water and acetonitrile, then cleaned up on C18-bonded silica SPE cartridges. The LOQ of this procedure was 10 ng/g. Urine samples were diluted, filtered, and analyzed directly. The LOQ of this procedure was 63 ng/mL. The overall accuracy for plasma was 103% with coefficient of variation (CV) of 3%; for kidney, 96% and 11%, respectively, and for urine, 98% and 4%, respectively. These methods were applied to the analysis of plasma, urine, and kidney biopsy samples taken from standing animals that had been dosed with penicillin.