SIMULTANEOUS GAS-CHROMATOGRAPHIC DETERMINATION OF METHAMPHETAMINE, AMPHETAMINE AND THEIR P-HYDROXYLATED METABOLITES IN PLASMA AND URINE

We report a method for the simultaneous determination of methamphetami ne, amphetamine and their hydroxylated metabolites in plasma and urine samples using a GC-NPD system. The analytical procedures are: (1) adj ust the sample to pH 11.5 with bicarbonate buffer, saturate with NaCl and extract with acetate; (2) back-extract the amines in the ethyl ace tate fraction with 0.1 M HCl; (3) adjust the pH of the acid fraction t o 11.5 and follow by extraction in ethyl acetate; (4) reduce the volum e of ethyl acetate under nitrogen and derivatize the concentrate with trifluoroacetic anhydride or heptafluorobutyric anhydride before the G C analysis. The derivatives were separated on a GC-NPD system equipped with a HP-5 column of 25 m X 0.32 m I.D. and a 0.52 mu m film of 5% p henylmethylsilicone. The detection limit (taking a signal-to-noise rat io of 2) of heptafluorobutyl derivatives of methamphetamine and its me tabolites in plasma and the trifluoroacetyl derivatives in urine was 1 ng/ml (22 pg on column). The limit of quantitation of the heptafluoro butyl derivatives in the plasma was 1 ng/ml (22 pg on column), and tha t of the trifluoroacetyl derivatives in urine was 20 ng/ml (73 pg on c olumn). The between-day variation was from 0.9 to 17.4% and within-day variation from 0.9 to 8.3%. This method was used successfully in the quantitative determination of methamphetamine and its p-hydroxylated m etabolites in the plasma and urine of human subjects.