Ionization Techniques SIMS, FAB, and MALDI

FIGURE 8.5 Schematic representations of desorption ionization techniques. 

The matrix should be nonvolatile, relatively inert, and a reasonable electrolyte to allow ion formation. If the matrix compound is more acidic than the analyte, then predominantly (M + H) ions will be formed, while mostly (M - H) ions will result when the matrix is less acidic than (he analyte. The matrix absorbs much of the excess energy imparted by the beam of ions/atoms and produces ions that contribute a large amount of background ions to the mass spectrum. In fact, chemical reactions within the matrix during ionization can contribute background ions in most mass 

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FIGURE 3.7 Common matrices for SIMS and FAB mass spectrometry. 

Picolinic acid 3-Hydroxypicolinic acid 2,5-Dihydroxybenzoic acid 

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