Laser spot size and laser power dependence of ion formation in high resolution MALDI imaging

Laser focus diameters (optical resolution) and dependence of ion signal intensities on laser fluence were investigated for MALDI imaging mass spectrometry at high spatial resolution (optical focus diameters in the range of 1.1-8.4 mu m). Results are of interest in the light of MALDI mechanisms and of methodological optimization, since no data was available yet for such small laser spots. The dependence of ion signal intensities on laser fluence was found to be in line with data published for larger laser spot diameters. Results argue for a common general mechanism in MALDI, with a steady trend of parameter values when going from larger (>100 mu m) to smaller (<10 mu m) spot sizes. (C) 2010 Elsevier B.V. All rights reserved.