Aspects of the Role of Surfaces in Ionization Processes

The operating principles and some applications of atmospheric pressure desorption electrospray ionization (DESI) and surface activated chemical ionization (SACI) methods are described in detail. The former technique allows one to obtain information on the chemical composition (in terms of organic compounds) present on a surface of interest. The latter, SACI, provides chemical information as a result of the interaction of a vaporised solution of the analyte with a metallic surface. Both techniques typically lead to the production of abundant protonated molecules. The data available in the literature indicate that both DESI and SACI are highly promising techniques with the former giving to mass spectrometry new application fields, and the latter an increasing sensitivity and a lowering of chemical noise that, in the case of biological samples, represent a weak point in many analytical measurements.