Electrospray mass spectrometry: a study on some aqueous solutions of metal salts.

Aqueous metal salt solutions were used as models to probe the origin of the species observed in the electrospray mass spectrum. A qualitative or semiquantitative correlation among different species was observed between electrospray responses and calculated equilibrium aqueous solution concentrations. Quantitative correlations were obtained, however, when ions that were identical in charge and similar in type were selected for comparison. In these experiments the ions experienced very similar electrospray-related processes and their effects on the responses were canceled in a comparison of these ions. Consequently, the relative abundances of these ions in the electrospray mass spectrum closely matched the calculated relative abundances in aqueous solution. Our results suggest that the basic principle that determines ionic distribution in the electro spray mass spectrum in aqueous solution chemistry.