Reduction of Cu(II) and Riboflavin in DIOS Mass Spectrometry

Understanding ion-molecular reactions is suggested to be essential to delineating the mechanisms of matrix-assisted laser desorption/ionization (MALDI) and related ionization methods. To examine the implications of matrix-analyte reactions in the reduction observed in MALDI, copper(II) chloride and riboflavin were analyzed by desorption/ionization on porous silicon (DIOS) mass spectrometry. This system does not require a matrix for soft laser desorption/ionization. The two susbstances were reduced by DIOS as well, and the reduction of riboflavin was accelerated using water as a solvent, as reported in MALDI. The results indicated that target-analyte electron transfer occurs in LDI, although the possibility of matrix-analyte electron transfer in MALDI cannot be excluded.