Matrix-assisted laser desorption mass spectra fragments

Since the signals are very short, simultaneous detection analysers or time-of-flight analysers are required. The probability of obtaining a useful mass spectrum depends critically on the specific physical proprieties of the analyte (e.g. photoabsorption, volatility, etc.). Furthermore, the produced ions are almost always fragmentation products of the original molecule if its mass is above approximately 500 Da. This situation changed dramatically with the development of matrix-assisted laser desorption ionization (MALDI) [17,18]. 

Chemical ionisation mass spectra (CIMS NHJ as ionisation reactant) can yield satisfactory spectra from underivatised peptides and field-desorption ionisation has been shown to give intense [M+ 1]+ ions from otherwise involatile peptide derivatives (for example, CH3—CO—Gly—Arg—Arg—Gly—OCH3 Buehler el al., 1974), but less sequence information is gained in these mild ionisation procedures because less fragmentation occurs and there are relatively few peaks in the mass spectrum. MALDF - matrix-assisted laser desorption ionisation MS - is an acronym that is encountered in recent literature for this ionisation technique. 

Figure 8 Positive ion matrix-assisted laser desorption (MALDI) time-of-flight mass spectrum of P-cryptoxanthin paknitate isolated from tangerine juice. Post source decay was used to enhance detection of structurally significant fragment ions such as loss of toluene (m/z 698), loss of palmitic acid (m/z 534), and loss of both toluene and palmitic acid (m/z 442). (From Ref. 320.)... 

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