DISCRIMINATION EFFECTS AND SENSITIVITY VARIATIONS IN MATRIX-ASSISTED LASER DESORPTION IONIZATION/

In matrix-assisted laser desorption/ionization (MALDI) the analyte sig nal produced depends strongly on the analyte and on the sample prepara tion procedure. Comparing the results obtained with the dried-drop met hod with the results obtained,vith a homogeneous sample preparation pr ocedure, discrimination effects, as web as sensitivity variations, are shown to be dependent on the molecular weight of the analysed compoun ds. The signal obtained in MALDI is shown to be dependent on the hydro phobicity and basicity of the analyte. With the dried-drop method, in particular, evidence of peripheral sample deposition of hydrophilic co mpounds is shown. These last effects are due to mass transfer caused b y differences in surface activities during solvent evaporation, and ar e known as Marangoni effects. (C) 1997 by John Wiley & Sons, Ltd.