Choosing an Appropriate Matrix

The MALDI matrix [38] has two important roles (i) to absorb the laser energy and (ii) to separate the analyte molecules from each other in order to avoid cluster formation. Consequently, the matrix and sample are normally prepared with between a 100- and 1000-fold molar excess of the matrix. An excess of the matrix also helps to avoid direct laser hits on the analyte that would lead to marked fragmentation. This effect can easily be seen if MALDI mass spectra are recorded with varying ratios between the analyte and matrix [29]. The most important 

Although many different compounds have been suggested as MALDI matrices, the analysis of lipids with their low molecular weights requires certain special properties of the matrix. For example, it is important that the yields of matrix (or matrix cluster) ions generated by laser irradiation are as low as possible. This is the reason why compounds that undergo photoreactions (especially matrices derived from cinnamic acid such as sinapinic add) should not be used, in order to avoid saturation of the detector by matrix-derived ions. 

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