Thermal Processes in Repetitive Laser Desorption Mass Spectrometry

Abstract

The laser-induced desorption of organic solids has been shown [1–4] to be essentially a rapid heating effect resulting in the flush evaporation of neutrals and ions which subsequently can undergo gas phase molecule — molecule/ion reactions, e.g. cationization. Although further types of irradiation interaction cannot be excluded, thermal effects must be assumed to play a major role. A recent investigation on supermolecular artefacts observed with repetitive laser desorption (RLD) [5] indicated that saccharides, due to their thermolability, may serve as a very sensitive probe for such thermal effects. As is known from carbohydrate chemistry [6], thermal degradation of saccharides in general occurs via formation of anhydrosugars, e.g. glucosans, which — among other reactions — strongly tend to polymerize. The generation of higher oligosaccharides/glycosides (by successive addition of anhydrosugar units) should thus be particularly indicative of thermal processes, regardless of the desorption technique applied. In order to investigate this aspect in more detail, the temperature dependence of the formation of such artefacts in RLD-experiments was studied.