Enhanced measurement of CsI cluster ions for mass calibration in MALDI-MS using sugar alcohols

Abstract

A simple method for measuring CsI cluster ions ((CsI)_nCs⁺ and (CsI)_nI⁻) from CsI₃ for mass calibration was developed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The application of CsI₃ with an additive, sugar alcohol (e.g., glycerol) or saccharide (e.g., dihydroxyacetone), on the MALDI plate resulted in an adequate series of CsI cluster ions within a mass range extending to over m/z 10 000 in the linear mode. The additives may be involved in improving the distribution of CsI₃ on the MALDI plate, thus aiding the effective measurement of cluster ions. Because of their ease in handling, CsI₃ and sugar alcohol or saccharide solutions comprised a suitable general-purpose mass calibrant for MALDI-MS instruments.