Identification of ephedrines as their carbon disulfide derivatives.

A method for the separation and identification of the diastereoisomers ephedrine and pseudoephedrine and the diastereoisomers norephedrine and norpseudoephedrine is presented. The compounds were derivatised by reaction with carbon disulfide in the presence of alkali. These derivatives and their trifluoroacetic anhydride derivatives were subjected to gas chromatography with nitrogen-selective detection as well as mass-selective detection and high-performance liquid chromatography with ultraviolet detection. The results showed that ephedrine and pseudoephedrine can easily be differentiated by gas chromatographic analyses of their carbon disulfide derivatives. Norephedrine and norpseudoephedrine can be differentiated by the different chromatographic retention times of their carbon disulfide derivatives and by the fact that norephedrine yielded two products and norpseudoephedrine only one product when reacted with carbon disulfide under the same conditions. Trifluoroacetylation of the latter compounds gave a more pronounced differentiation.