Liquid chromatographic chiral stationary phases in pharmaceutical analysis: determination of trace amounts of the (-)-enantiomer in (+)-amphetamine.

A rapid and accurate method was developed for the determination of the enantiomeric composition of amphetamine preparations. Amide derivatives of the amphetamine enantiomers are first formed by using achiral 2-naphthoyl chloride. The resulting enantiomeric amides are then chromatographed on a commercially available chiral stationary phase. The capacity factors (k') of (-)- and (+)-2-naphthoylamphetamine are 20 and 22, respectively, and the separation factor (alpha) for the two enantiomers is 1.08. The method allows detection of as little as 0.5% of the (-)-enantiomer in (+)-amphetamine and is applicable to both bulk drug and single-tablet analyses.