Chiral identification and determination of ephedrine, pseudoephedrine, methamphetamine and methcathinone by gas chromatography and nuclear magnetic resonance.

The enantiomers of the related substances methamphetamine, ephedrine, pseudoephedrine and methcathinone were determined by both gas chromatography after derivatization and by nuclear magnetic resonance using a chiral solvating agent. For GC the substances were derivatized with (R)-(+)-alpha-methoxy-alpha-(trifluoromethyl)phenylacetic acid (MTPA) to give diasteromeric derivatives. Resolution (baseline) of at least 1.6 was obtained between all derivatives. NMR determination of the enantiomers was conducted in a chiral environment by the addition of the chiral solvating agent, (R)-(+)-1,1'-bi-2-naphthol, to NMR solutions of the substances. Racemization of methcathinone was demonstrated to be facile by exposure to alkaline solutions for varying periods of time. Enantiomeric ratios of some products derived from the oxidation of ephedrine were determined.