The Fragmentation of Amine Cluster Ion Including HCl
-Proton Affinities of Drugs of Abuse-

Abstract

The fragmentation of the cluster ion, [A₁+HCl+A₂+H]⁺ of amine bases A₁ and A₂, is studied by the BEBE type tandem mass spectrometer. The cluster ion, [A₁+HCl+A₂+H]⁺, is generated by the fast atom bombardment (FAB) ionization of mixture of two hydrochlorides of amines. The precursor ion is selected by the first analyzer (BE) and the product ions are scanned by the second analyzer (B/E linked scanning). The fragmentation of [A₁+HCl+A₂+H]⁺ yields two protonated monomers, [A₁+H]⁺, [A₂+H]⁺, and protonated heterodimer, [A₁+HCl+A₂+H]⁺. The relative abundances of [A₁+H]⁺ and [A₂+H]⁺ from the fragmentation of [A₁+HCl+A₂+H]⁺ are found to be related to their relative proton affinities and are used to determine the proton affinities (PAs) of methamphetamine and its analogs. The PA of methamphetamine is estimated to be 965 kJ/mol.