Gas-Phase Potassium Binding Energies of MALDI Matrices: An Experimental and Theoretical Study

Abstract

Gas-phase potassium binding free energies of four aromatic molecules, which are used as matrices in the matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, were determined experimentally by the ligand-exchange equilibrium method in a Fourier transform ion cyclotron mass spectrometer (FT ICR MS). The matrices studied were 2,5-dihydroxybenzoic acid, 2,4,6-trihydroxyacetophenone, trans-3,5-dimethoxy-4-hydroxycinnamic acid, and 1,8,9-trihydroxyanthrancene. In addition to the experimental values, we also present quantum chemical results obtained by the density functional theory (DFT) at the 6-31+G* level. The gas-phase potassium binding free energies of the MALDI matrices studied in this work are in the range of 90−105 kJ mol-1.