Reduction of nitriles to amines in positive ion electrospray ionization mass spectrometry

Some compounds readily form [M+46]+ adduct ions during positive ion electrospray ionization mass spectrometry ((+)ESI-MS) analysis. These [M+46]+ ions were characterized as [M+CH3CH2NH2+H]+ by accurate mass determination. Ethylamine involved in the adduct was proposed to be the reduction product of acetonitrile and this was confirmed using deuterated acetonitrile. Other nitrile-containing compounds tested, including isobutyronitrile and benzonitrile, also formed the adduct ions of the respective amine forms under (+)ESI-MS conditions. Hydrogen/deuterium exchange experiments demonstrated that the reductive hydrogen originated from water. Reduction of nitriles (R-CN) to their respective amines (R-CH2NH2) under (+)ESI-MS conditions expands the ability to identify nitrile-containing chemical unknowns.