Determination of cocaine and benzoylecgonine in guinea pig's hair after a single dose administration by LC-MS/MS.

A sensitive LC-MS/MS method to determine cocaine and its major metabolite benzoylecgonine in guinea pig' s hair has been established. About 20 mg of decontaminated hair sample was hydrolyzed with 0. 1 mol x L(-1) HCl at 50 degrees C overnight, in the presence of cocaine-d3 and benzoylecgonine-d8 used as internal standards, and then extracted with dichlormethane. The analysis was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Positive electrospray ionization (ESI +) and multiple reactions monitoring (MRM) mode were used. The limit of detection (LOD) for cocaine and benzoylecgonine was 1 pg x mg(-1). The calibration curves of extracted standards were linear over the range from 5 pg x mg(-1) to 250 pg x mg(-1) (r2 > or = 0.9997). The method was validated and applied to the analysis of guinea pig's hair after a single dose administration of cocaine hydrochloride. Cocaine and benzoylecgonine were not only detected, but also quantified in guinea pigs hair.