Development of a liquid chromatography-tandem mass spectrometric method for the determination of methamphetamine and amphetamine using small volumes of rat serum

The aim of this paper was to develop LC/MS/MS methodology for the determination of methamphetamine (METH) and amphetamine (AMP) using low microliter volumes (20-150 microl) of rat serum and demonstrate the use of this method for the study of serum pharmacokinetics in the rat. The analytes were extracted from rat serum using solid-phase extraction followed by an isocratic separation on a narrow-bore Hypersil C(18) column. Lower limits of quantitation for METH and AMP were 0.3 ng/ml using positive ion electrospray tandem mass spectrometry. The accuracy of the method was within 20% of the actual values over a wide range of serum concentrations. The within-day and between-day precision was better than 20% (R.S.D.). Ion-suppression matrix effects on electrospray ionization were evaluated for extracted rat serum. The LC/MS/MS method was further validated by comparing serum concentrations of METH and AMP to serum concentrations previously determined using an LC/ (3)H]-METH assay with radiochemical detection. Finally, the LC/MS/MS method was used to study the pharmacokinetics of METH and AMP after a 1mg/kg intravenous bolus dose of METH to female Sprague-Dawley rats.