A perspective on MALDI alternatives-total solvent-free analysis and electron transfer dissociation of highly charged ions by laserspray ionization

Abstract

Progress in research is hindered by analytical limitations, especially in biological areas in which sensitivity and dynamic range are critical to success. Inherent difficulties of characterization associated with complexity arising from heterogeneity of various materials including topologies (isomeric composition) and insolubility also limit progress. For this reason, we are developing methods for total solvent-free analysis by mass spectrometry consisting of solvent-free ionization followed by solvent-free gas-phase separation. We also recently constructed a novel matrix-assisted laser desorption ionization (MALDI) source that provides a simple, practical and sensitive way of producing highly charged ions by laserspray ionization (LSI) or singly charged ions commonly observed with MALDI by choice of matrix or matrix preparation. This is the first ionization source with such freedom-an extremely powerful analytical 'switch'. Multiply charged LSI ions allow molecules exceeding the mass-to-charge range of the instrument to be observed and permit for the first time electron transfer dissociation fragment ion analysis.