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Pyrolysis-membrane inlet mass spectrometry has been used to investigate the oxidative products of several peptides in an air buffered quadrupole ion trap mass spectrometer. Results indicate that ion-molecule reactions can occur with solvent species present, forming adducts in the mass spectrometer. In addition, products resulting from oxidative pyrolysis may appear to be ion-molecule additions. Using isotopically labeled standards, different buffer gases and tandem mass spectrometry, two major oxidation products were determined to occur from proteins. Tyrosyl and phenylalanyl residues present in peptides and proteins were found to produce p -methoxybenzaldehyde and benzaldehyde upon oxidative thermal degradation. Subsequent analyte enhancement by the membrane inlet produced large mass spectral peaks characteristic of these amino acid species, when present. This paper details the investigation into the source and mechanism leading to the formation of some of these products. |
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