GC-MS studies on side chain regioisomers related to substituted methylenedioxyphenethylamines: MDEA, MDMMA, and MBDB.

Three regioisomeric 3,4-methylenedioxyphenethylamines having the same molecular weight and major mass spectral fragments of equal mass have been reported as drugs of abuse in forensic studies in recent years. These compounds are 3,4-methylenedioxy-N-ethylamphetamine (MDEA), 3,4-methylenedioxy-N,N-dimethylamphetamine (MDMMA), and N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB). A series of seven additional side chain regioisomers have mass spectra essentially equivalent to the three controlled drug substances, all have molecular weight of 207 and major fragment ions in their electron ionization mass spectra at m/z 72 and 135/136. The trifluoroacetyl, pentafluoropropionyl, and heptafluorobutryl derivatives of the primary and secondary regioisomeric amines were evaluated in GC-MS studies. The mass spectra for these derivatives were significantly individualized, and the resulting unique fragment ions allowed for specific side chain identification. The trifluoroacetyl and heptafluorobutryl derivatives provided more specific fragment ions for molecular individualization among these regioisomeric substances. These perfluoroacyl derivatives showed reasonable resolution on the polar stationary phase Rtx-200.