On initial ion velocities in MALDI: A novel FT-ICR MS approach

Even after more than two decades of investigation, the question whether the initial velocity of ions generated by matrix-assisted laser desorption/ionization (MALDI) depends on their molecular weight or not remains unanswered. A novel method employing an internal MALDI source Fourier-transform ion cyclotron resonance mass spectrometry is used to measure the initial ion velocities of peptides with m/z values in the range of typical proteomic experiments. Simultaneous measurement of multiple matrix and analyte ions clearly shows initial ion velocities that depend on analyte or matrix molecular weight. The measured velocity values agree well with the published data. (C) 2014 Elsevier B.V. All rights reserved.