Effect of cationization reagents on the matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum of Chinese gallotannins

In this study, Chinese gallotannins were characterized by MALDI‐TOF MS, and effects of cationization reagents on the quality of spectra were investigated. The trideca‐ and tetradeca‐galloyl glucoses were observed in Chinese gallotannins, which could not be detected in earlier studies. When Cs+ was used as the cationization reagent, Chinese gallotannins gave a relatively simple MALDI‐TOF spectrum, three series of quasimolecular ions [M + Cs]+, [M + 2Cs–H]+, and [M + 3Cs–2H]+ and a series of metastable ion peaks with minimum abundance were detected. Selection of Na+ as the cationization reagent, additional three series of ion peaks including two patterns from the fragmentation and complex 2M adducts [2M + Na]+ can be distinguished. In the case of no deionization or addition of cationization reagent to the analyte/matrix, naturally abundant Na+ and K+ as the cationization reagent, [M + Na]+ and [M + K]+ molecular ions both appeared in the complicated spectrum. Therefore, we conclude that cationization reagents affect the MALDI‐TOF MS spectrum of Chinese gallotannins significantly.