GC-MS, MS/MS and GC-IR Analysis of a Series of Methylenedioxyphenyl-Aminoketones: Precursors, Ring Regioisomers and Side-Chain Homologs of 3,4-Methylenedioxypyrovalerone

Chromatographic retention increased with the hydrocarbon content of the alkyl side-chain, and the 3,4-methylenedioxy substitution pattern showed higher retention than the corresponding 2,3-methylenedioxy isomer. The aminoketones showed major peaks in their mass spectra corresponding to the homologous series of iminium cation fragments from the loss of the regioisomeric methylenedioxybenzoyl radical species. Deuterium labeling experiments confirm the iminium cation base peaks to undergo the loss of a hydrocarbon molecular fragment to yield product ions characteristic of the side-chain and pyrrolidine ring portion of the parent cathinone derivative. The mass spectra for the designer drug MDPV and its regioisomeric 2,3-methylenedioxy isomer showed equivalent fragments, including the base peak at m/z 126 and major product ion fragments at m/z 84. The ring substitution pattern for these two isomers was differentiated by characteristic absorption bands in the 1,500 -1,200 cm-1 range in their vapor phase IR. These characteristic bands can also be used to identify the aromatic ring substitution pattern in the regioisomeric precursor ketones. (Publisher abstract modified)