Simple and sensitive high-performance liquid chromatographic determination of methamphetamines in human urine as derivatives of 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride, a new fluorescence derivatization reagent.

A simple, rapid and highly sensitive high-performance liquid chromatographic method for the determination of methamphetamine and its metabolites in human urine was developed. Without tedious pretreatment procedures, aliquots of methamphetamine spiked or abusers' urine samples were simply acidified, dried under a stream of N2 gas, and then derivatized with 4-(4,5-diphenyl-1H-imidazol-2-yl) benzoyl chloride in acetonitrile in the presence of traces of triethylamine. Five derivatives were isocratically separated within 33 min by an ODS column, and the effluent was monitored at 440 nm (lambda(ex), 330 nm). Using 1-phenylethylamine as an internal standard calibration curves were confirmed to be linear up to at least 2x10(-5) M in urine with correlation coefficients of 0.998-1.000, while the detection limits at S/N=3 were 0.6-5.2 fmol per 5-microl injection. The relative standard deviations (n=5) of inter- and intra-day variations were less than 8.9%. The correlation between the concentrations of methamphetamine and amphetamine in urine determined by the proposed method and another currently accepted one was satisfactory. The method was successfully applied to urine samples collected from methamphetamine addicts.