δ13C, δ15N and δ2H isotope ratio mass spectrometry of ephedrine and pseudoephedrine : application to methylamphetamine profiling

Conventional chemical profiling of methylamphetamine has been used for many years to determine the synthetic route employed and where possible to identify the precursor chemicals used. In this study stable isotope ratio analysis was investigated as a means of determining the origin of the methylamphetamine precursors, ephedrine and pseudoephedrine. Ephedrine and pseudoephedrine may be prepared industrially by several routes. Results are presented for the stable isotope ratios of carbon (δ13C), nitrogen (δ 15N) and hydrogen (δ2H) measured in methylamphetamine samples synthesized from ephedrine and pseudoephedrine of known provenance. It is clear from the results that measurement of the δ13C, δ15N and δ13H stable isotope ratios by elemental analyzer/thermal conversion isotope ratio mass spectrometry (EA/TC-IRMS) in high-purity methylamphetamine samples will allow determination of the synthetic source of the ephedrine or pseudoephedrine precursor as being either of a natural, semi-synthetic, or fully synthetic origin.