Electrospray MS-based characterization of beta-carbolines--mutagenic constituents of thermally processed meat.
The beta-carbolines 1-methyl-9H-pyrido 3,4-bindole and 9H-pyrido3,4bindole have been implicated as having causative roles in a number of human diseases, such as Parkinsons disease and cancer. As they can be formed during the heating of protein-rich food, a number of analytical methodologies have been proposed for their detection and quantification in foodstuff. For this purpose, LC-MS and LC-MSMS have emerged as the most specific analytical methods, and the quantification is based on the occurrence of unusual ions, such as MH-(H()) and MH-2H. In this study, we have investigated the formation of these ions by accurate-mass electrospray MSMS and demonstrated that these ions are formed from gas-phase ion-molecule reactions between water vapor present in the collision cell and the protonated molecule of 1-methyl-9H-pyrido 3,4-bindole and 9H-pyrido3,4bindole. Although this reaction has been previously described for heterocyclic amine ions, it has been overlooked in the most of recent LC-MS and LC-MSMS studies, and no complete data of the fragmentation are reported. Our results demonstrate that additional attention should be given with respect to eliminating water vapor residues in the mass spectrometer when analysis of beta-carbolines is performed, as this residue may affect the reliability in the results of quantification.