Determination of enantiomeric amphetamines as metabolites of illicit amphetamines and selegiline in urine by capillary electrophoresis using modified β-cyclodextrin

The determination of enantiomeric amphetamine and methamphetamine in urine samples is important in order to distinguish use of the prescription drug selegiline (metabolized to R(−)-A and R(−)-MA) from the illicit use of S(+)-A and S(+)-MA. For the analysis of enantiomeric amphetamine (A) and methamphetamine (MA) in biological samples, the optimization of analytical condition was performed by capillary electrophoresis using chiral selectors including β-cyclodextrin, carboxymethyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin. We have examined the factors to obtain the best chiral resolutions, separation efficiency and sensitivity, and wide concentration linearity. Optimum resolutions were achieved using 100 mM phosphate buffer, pH 2.5, containing 10 mM of carboxymethyl-β-cyclodextrin. This method was applied for the quantitative determination of enantiomeric amphetamine and methamphetamine in urine samples obtained from patients taking illicit amphetamines or from rats and patients taking selegiline. Acceptable quantitative results in terms of resolution, precision, sensitivity and linearity were obtained from the real urine samples containing wide-ranging concentrations of A and MA by using two concentrations of internal standards, α(+)- (1 μg/ml) and β-phenylethylamine (50 μg/ml).