Alkali ion impurities

Note Carbohydrates possess a high affinity towards alkali metal ions, and thus in MALDI spectra [M-tNa] and/or [M+K] are normally observed instead of or in addition to [Mh-H]" ions of very low abundance. Radical ions are not observed. It basically depends on the relative amount of alkali ion impurities or dopant which quasimolecular ion will be dominant. 

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