The analysis of enantiomeric and diastereoisomeric mixtures of ephedrine and pseudoephedrine using reversed-phase HPLC of nickel dithiocarbamate complexes.

Abstract

Following their conversion to dithiocarbamate ligands and thence to nickel complexes, enantiomeric mixtures of ephedrine or pseudoephedrine may be separated and quantitated by reversed-phase High Performance Liquid Chromatography (HPLC) using ternary solvent mixtures. The solvent used to dissolve the complexes prior to injection was found to have a significant effect on the separation. In a similar manner, a mixture of the diastereoisomers ephedrine and pseudoephedrine was separated and quantitatively analysed using a binary solvent as the mobile phase. This separation was achieved both with prior formation of the nickel complexes and also with on-column formation using nickel(II) ions in the mobile phase. The analysis of diastereoisomeric contaminants in pharmaceutical products and raw materials containing ephedrine or pseudoephedrine is illustrated.