Mass spectrometry distinguishing C=C location and cis/trans isomers: A strategy initiated by water radical cations

We present an approach for the elucidation of C=C bond position and cis/trans isomers, which is achieved by the reaction of ambient water radical cations and double bonds, followed by the fragmentation of epoxide radical cations to generate diagnostic ions in tandem mass spectrometry. Hexenol double bond positional isomers and cis/trans isomers which exhibit different properties and biological functions are characterized as a proof of concept. The merits of the approach include the simplicity of experimental setup, rapid derivatization (within seconds), the obviation of organic solvents, as well as easy spectral interpretation. [Display omitted] •A novel approach for the elucidation of C=C bond position and cis/trans isomers.•In situ epoxidation reaction of ambient water radical cations and C=C bonds.•No need of special instrumentation and organic solvents.