Chemical reactions at interfaces: Hydrogen-deuterium exchange using a solid ND4Cl matrix in molecular secondary ion mass spectrometry

Organic compounds containing active hydrogens (e.g. imino, amino, carboxylic acid and hydroxy functional groups) undergo hydrogen–deuterium (H–D) exchange reactions in the course of argon ion bombardment in molecular secondary in mass spectrometry (SIMS) when examined as solids in solid ND4Cl matrix. The positive‐ion SIMS spectra of non‐ionic compounds (M) display ions resulting from exchange of active hydrogens in both the deuterated ((M + D)+) and cationized ((Ag + M)+ and (C+ + M)+) forms, while ionic compounds display exchange products in the intact cation (C+, where C = cation). Analogous H–D exchange is observed in the negative SIMS spectra of compounds bearing active hydrogen atoms. The fact that the exchange reactions are dependent on the primary ion dose demonstrates that they occur in the energized sample and not prior to ion bombardment. Information on the mechanisms of interfacial reactions, insights into the SIMS mechanism and confirmation of the number of acidic hydrogens in non‐volatile organic ompounds are revealed by this experiment.