Direct mass spectrometric analysis of thermally labile and nonvolatile molecules, like many of the anthocyanins and other phenolic compounds, has not always been possible. In the days of EI and CI it was necessary to derivatize these molecules before obtaining mass spectrometric data. However, with the advent of soft ionization techniques - initially fast atom bombardment (FAB; Fenselau, 1983) and plasma desorption (PD; Sundqvist and Macfarlane, 1985) - followed by the development of electrospray ionization (ESI; Cole, 2000) and matrix-assisted laser desorption ionization (MALDI; Zenobi and Knochenmuss, 1998), the mass spectrometry of these compound classes became possible, even routine. These techniques provide molecular weight information through formation of (M+H)+ or (M+Na)+ ions, or in the case of pre-charged ions like anthocyanins, the cations themselves. Mass spectrometry not only provides information on the molecular weight of a compound of interest, but with the advent of tandem mass spectrometric techniques structurally significant information can also be generated. In tandem mass spectrometry (ms/ms) the ion of interest is selected and given excess energy. This can be done in a variety of ways, including collisions with neutral atoms (Busch et al., 1988). The excited molecule can then undergo fragmentation, with the resulting ions providing structural information about the original precursor ion.
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