THE EFFECTS OF MATRIX PH AND CATION AVAILABILITY ON THE MATRIX-ASSISTED LASER-DESORPTION IONIZATION MASS-SPECTROMETRY OF POLY(METHYL METHACRYLATE)

The matrix-assisted laser desorption/ionization (MALDI) of poly(methyl methacrylate) has been studied using time-of-flight (TOF) mass spectr ometry. The effect of pH was investigated through titration of the mat rix, The presence of doped alkali metal cations produced shifts in the polymer molecular weight distribution of as much as 20%, Results indi cate that careful control of experimental conditions is needed to obta in reproducible mass spectra of synthetic polymers, and to critically evaluate the accuracy of polymer-size distributions measured by MALDI- TOF mass spectrometry, as the role of the matrix in desorption and ion ization processes is not yet fully understood.