A study of cation attachment to polystyrene by means of matrix-assisted laser desorption/ionization and electrospray ionization-mass spectrometry

A range of metal cations has been shown, by means of matrix assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, to form adduct complexes with polystyrene. Both MALDI and ESI mass spectra contain adduct ion peaks corresponding to [PS + Cat]⁺, where PS represents a polystyrene molecule and Cat a cationic species. In addition, salt cluster complexes assigned as [PS + M(MX)(n)]⁺, where MX represents the metal salt, M the metal cation and n = 1 or 2, are observed in ESI spectra. The most favourable interaction between cation and polymer, for MALDI experiments involving dithranol as the matrix, occurs when either silver or copper ions are the dopant cations, whereas the addition of potassium salts leads to the most intense and reproducible ESI spectra. It has been established that there are several problems associated with the analysis of synthetic polymers in an ESI-quadrupole instrument which are not found in the corresponding MALDI-TOF experiments.