Abstract
Mass spectra of ethylenediaminetetraacetic acid (EDTA) were obtained using electron ionization (EI), chemical ionization (CI) and fast atom bombardment (FAB). Thermal degradation was observed in both EI and CI. It was nevertheless possible to obtain reproducible spectra and characteristic peaks at 125°C probe temperature. In FAB, protonated EDTA ions were observed only if the matrix was acidified. Selection of matrices also influences the [M + H]+ signal in acidic solution, the best results being obtained with the matrix glycerol. The influence of pH becomes more evident for EDTA in HCl solutions of different concentration. These results seem to indicate an important role for protonated [M + H]+ species in solution prior to gaseous ion formation by FAB. The main effect of acid seems to be a solubility effect, although surface activity may also play a role.
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