ON THE MECHANISM AND CONTROL OF SALT-INDUCED RESOLUTION LOSS IN MATRIX-ASSISTED LASER DESORPTION IONIZATION/

The effects of salt impurities in matrix-assisted laser desorption/ion ization were studied. It was observed that, when metal cations are pre sent in the sample, they can induce clustering between matrix and anal yte molecules. Such cluster-adducts can lead to loss of mass resolutio n, especially for high molecular weight analytes, such as proteins, an d for samples where salts are naturally present. The evidence indicate s that these cluster-adducts are formed in the matrix, before desorpti on. Acidic preparation conditions and a high polarity solvent can sign ificantly reduce clustering and therefore improve mass resolution and accuracy.