In this study, a series of 12 isomeric phenethylamines were evaluated by gas chromatography, using vapor phase infrared spectrophotometric detection.
The major mass spectral fragments for each of these unique isomers occur at equivalent mass and all have equal molecular weight. The infrared spectra for these compounds enabled the identification of any one of these amines to the exclusion of all other isomers. This differentiation was accomplished without the need for chemical derivatization. The methoxymethcathinones showed unique infrared absorption bands in the 1690–1700 cm−1 range for the carbonyl group, and the ring substitution pattern in the ethoxymethamphetamines can be differentiated by several bands in the 700–1610 cm−1 region. Side chain and degree of nitrogen substitution can be evaluated in the 2770–3000 cm−1 region of the infrared range. All the studied regioisomers could be differentiated from 3,4-MDMA via their vapor phase IR spectra. Capillary gas chromatography on an Rxi-50 stationary phase successfully resolved the side chain regioisomers, the substituted methamphetamines, and the methoxymethcathinones. (publisher abstract modified)