Ion–molecule reactions of charged thiols with neutral epoxides in the collision cell of a tandem quadrupole mass spectrometer. A model for invivo biomolecule reactions

Abstract

Gas-phase ion‐molecule chemistry has been used to study the reactions of mutagenic epoxides toward sulfur-containing (SH) organic chemicals. Reactions are selectively observed between mass-selected radical ions of thiols and neutral epoxides in the collision cell (Q2) of a tandem quadrupole mass spectrometer. A daughter-ion scan function is used to produce associative reaction product spectra by scanning the third quadrupole upward from the m/z value of the molecular ion of the sulfur-containing reagent ion. Optimal product yields are obtained by varying the collision cell energy from +1 to ‐5 V. It was observed that gas-phase product formation proceeded in a manner analogous to acidic solution chemistry (e.g. via the protonated epoxide) and that the product spectrum was sensitive to the structure of both the thiol radical-ion and the neutral epoxide. Q2 gas-phase reactions represent, therefore, a potentially new analytical technique to identify selectively chemicals in a gas stream (e.g. gas chromatography effluent) the toxicity of which are defined by their reactivity as electrophiles with nucleophilic sites in biomolecules.