Application of chiral lanthanide nuclear magnetic resonance shift reagents to pharmaceutical analysis. II. Determination of dextro- and levoamphetamine mixtures.

Optically pure d- and l-amphetamine sulfate, as well as various mixtures of the 2 enantiomers, were analyzed using a europium chiral nuclear magnetic resonance shift reagent. The enantiomeric shift difference (delta delta delta) exhibited by the doublet associated with the alpha-methyl protons was large enough to differentiate between the levo- and dextro-isomers. The alpha-methyl protons were decoupled and the enantiomeric composition was determined by using the peak heights of the resulting singlets. As little as 5% of the levo-isomer in the presence of the dextro-isomer can be determined using this method. The method is applicable to the analysis of bulk drug and pharmaceutical preparations.