MALDI INDUCED SATURATION EFFECTS IN CHEVRON MICROCHANNEL PLATE DETECTORS

Pulsing the gain from a low level to a high level is an effective way to reduce or eliminate saturation of a chevron microchannel plate dete ctor struck by large numbers of low molecular weight ions, such as the matrix ions generated in matrix-assisted laser desorption-ionization events. In this study, we used a switching circuit to vary the initial voltage across the first microchannel plate from 37 to 100% of its fi nal, full-gain voltage. This has enabled us to examine microchannel pl ate saturation over a broader range of gain than any previously report ed. Experiments with a proteolytic digest of a protein clearly demonst rate that apart from the matrix ions, the ions from a lower mass molec ule in a mixture can make it more difficult or even impossible to dete ct signals from larger molecules originating from the same mixture. Co mposite spectra, which might provide a more complete accounting of the compounds present in a mixture, can be easily produced by varying the switching delay in steps during the course of acquisition, (C) 1997 E lsevier Science B.V.