Factors contributing to peak broadening and mass accuracy in the characterization of intact spores using matrix-assisted laser desorption/ionization coupled with time-of-flight mass spectrometry

Factors contributing to peak broadening, accuracy and precision in mass ass ignment in the matrix-assisted laser desorption/ionization characterization of a lipopeptide desorbed from intact Bacillus spores were investigated. T hese spores were studied as an example of a thick, topologically irregular sample, which present a more difficult target than a pure peptide or protei n. The type of matrix, matrix:sample ratio, laser fluence, and localized re petitive laser irradiation were all found to affect the full-width at half maximum of the biomarker. Both in-source and post-source phenomena were sho wn to contribute. Sample thickness had less effect. Precision and accuracy of mass assignment were also affected by matrix:sample ratio and laser flue nce. In general, this sample was responsive to the same experimental variab les as pure peptides, and the use of an internal standard produced signific ant improvements in precision and accuracy. Copyright (C) 2001 John Wiley & Sons, Ltd.