IRMPD spectroscopy of metal cationized ions generated by MALDI source with graphene as the matrix

•A new strategy to obtain IRPD spectra of complex ions generated by MALDI.•The method is combined with H/D exchange to identify the chromophores.•Ions of [Arg + Rb]+ generated by MALDI are hotter than those generated by ESI.

A new strategy to obtain IRMPD spectra of metal cationized ions by combining MALDI and IRMPD methods is presented here, in which graphene is selected to be the matrix to generate the metal cationized ions. [Arg + Rb]+ were studied here as the sample ions. Based on the experiential IRMPD spectrum and theoretical calculations, it is suggested that the ions of [Arg + Rb]+ generated here had more internal energies than those generated by ESI method reported previously by Williams et al. (J. Phys. Chem. A 2007, 111, 11759-11770). The method is also combined with the H/D exchange to identify the chromophores for the observed IR peak. The method provides a new way to obtain structural information of metal cationized ions, and also makes the identification of isomeric compounds feasible.

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