Effects of sample preparation on matrix-assisted laser desorption/ionization time-of-flight mass spectra for sodium polystyrene sulfonate

Studies have been made on the influence of matrix concentration and the selection of matrix-solvent combinations for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Sodium polystyrene sulfonate (SPS) with five different degrees of polymerization, Mw = 1640, 4950, 7950, 16 600 and 57 500, were studied. The matrix 2′,3′,4′-trihydroxyacetophenone (THAP) was selected and was combined with acetonitrile, methanol, 2-propanol or water as the solvent. The MALDI-TOF experiments in negative ion mode reveal the following observations: (1) The concentration of the matrix must be increased as the degree of the polymerization increases; (2) depending on the degree of polymerization, there are different optimum combinations between the matrix and the polymer samples, and (3) different polarity of the solvents used in the matrix (THAP) preparation result in different MALDI spectra.