Measurements of initial velocity in matrix assisted laser desorption/ionization (MALDI) and identification of wheat varieties using MALDI-TOF

The results of initial velocity measurements of matrix and analyte in the MALDI plume, and, wheat variety identification by the gliadin spectrum using MALDI-TOF, and are reported. A reflecting Time-of-flight mass spectrometer with delayed extraction (Manitoba TOF II) was used for both measurements of the discussed experiments.;Information on the initial speed of MALDI ions can provide more clues to the nature of the MALDI process, as well as give corrections to m/z for linear instruments. Previous initial velocity results showed a discrepancy of values between different methods used. The results here using a technique based on delayed extraction in a reflecting TOF instrument found an average initial velocity of 660 m/s for proteins, and velocities higher than 1000 m/s for matrix ions. These results are consistent with earlier measurements made by a simpler DC technique where ions are desorbed into a field free region prior to acceleration. These results do not correspond to a previous experiment using delayed extraction to measure initial velocities. That experiment did not use a mirror to preserve peak resolution as ours did. The velocity values of the previous delayed extraction experiment were approximately a factor of two lower than the field free and the ones presented here, suggesting possibly a source of systematic error was present in that experiment. (Abstract shortened by UMI.)...