The Analysis of Enantiomeric and Diastereoisomeric Mixtures of Ephedrine and Pseudoephedrine Using Reversed-Phase High Performance Liquid Chromatography of Nickel Dithiocarbamate Complexes

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Abstract
Following their conversion to dithiocarbamate ligands and thence to Ni complexes, enantiomeric mixtures of ephedrine or pseudoephedrine [antihistamines] 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 had a significant effect on the separation. In a similar manner, a mixture of the diastereoisomers ephedrine and pseudoephedrine was separated and quantitatively analyzed by using a binary solvent as the mobile phase. This separation was achieved both with prior formation of the Ni complexes and with on-column formation using Ni2+ in the mobile phase. The analysis of diastereoisomeric contaminants in pharmaceutical products and raw materials containing ephedrine or pseudoephedrine is illustrated.