Chemical reactivity in matrix-assisted laser desorption/ionization mass spectrometry

During the control of a multistep organic synthesis on a soluble polymer (PEG) by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, a chemical reactivity was encountered when the matrix was acidic, for the samples where the amino moiety of the anchored compounds was protected as a Schiff base. Such imine hydrolysis was proven to be solely mediated by the acidic matrix during analyses since the expected protected structures were detected when the experiments were duplicated with a non-acidic matrix. Even if MALDI mass spectrometry was found to be more convenient than electrospray ionization mass spectrometry for the monitoring of liquid phase organic syntheses, the chemical reactivity imparted by the use of a matrix must be taken into account to avoid erroneous spectra interpretations. Copyright 1999 John Wiley & Sons, Ltd.