Application of nonpolar matrices for the analysis of low molecular weight nonpolar synthetic polymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The application of nonpolar matrices for the analysis of low molecular weig ht nonpolar synthetic polymers using matrix-assisted laser desorption/ioniz ation mass spectrometry (MALDI-MS) is demonstrated. Anthracene, pyrene, and acenaphthene were utilized as nonpolar matrices for the analysis of polybu tadiene, polyisoprene, and polystyrene samples of various average molecular weights ranging from about 700 to 5000. The standard MALDI-MS approach for the analysis of these types of polymers involves the use of conventional a cidic matrices, such as all-trans-retinoic acid, with an additional cationi zation reagent. The nonpolar matrices used in this study are shown to be as equally effective as the conventional matrices. The uniform mixing of the nonpolar matrices and the nonpolar analytes enhances the MALDI-MS spectral reproducibility. Silver salts were found to be the best cationization reage nts for all of the cases studied. Copper salts worked well for polystyrene, poorly for polyisoprene, and not at all for polybutadiene samples. These m atrices should be useful for the characterization of hydrocarbon polymers a nd other analytes, such as modified polymers, which may potentially be sens itive to acidic matrices. (J Am Soc Mass Spectrom 2000, 11, 731-737) (C) 20 00 American Society for Mass Spectrometry.