Differentiation of Homologous and Regioisomeric Methoxy-Cathinone Derivatives by GC-MS, MS/MS and GC-IR

Nine homologous and regioisomeric methoxyphenyl-aminoketone cathinone derivatives were prepared from the three commercially available 2-, 3- and 4-methoxybenzaldehydes. The gas chromatographic separation of the nine precursor methoxyphenones was achieved on a 100 percent dimethyl polysiloxane (Rtx-1) stationary phase and the regioisomeric aminoketones were resolved on a 5 percent diphenyl, 95 percent dimethyl polysiloxane (Rtx-5) stationary phase. The chemical ionization mass spectra (CI-MS) show only one major peak occurring at the mass of the protonated molecular ion (M + 1)+ while the EI-MS spectra display primarily the iminium cation fragment. The MS/MS product ion spectra for the three homologous iminium cations yield a homologous series of ions representing the loss of 42 Da from the parent species. MS/MS experiments confirmed the loss of 42 Da occurring via pyrrolidine ring fragmentation for iminium cations having the methyl and ethyl side-chains and via side-chain fragmentation for the n-propyl side-chain. The vapor phase infrared spectra in the range of 1300-1150 cm-1 show unique and characteristic absorption pattern for each of the three regioisomeric methoxy-group substitution patterns. 1 graphical abstract (Publisher abstract modified)