Qualitative assessment of monomer ratios in putative ionic terpolymer samples by electrospray ionization mass spectrometry with collision-induced dissociation.

Collision-induced dissociation in the source of an electrospray (ES) mass spectrometer was employed to characterize putative samples of the ionic terpolymer poly(styrene sulfonate-co-acrylic acid-co-2-acrylamido-2-methyl-1-propanesulfonic acid). Qualitative and semi-quantitative information about the monomer content was quickly obtainable from ES spectra, and indicated that some samples contained little or none of one or two expected comonomers. For two representative samples, confirmatory nuclear magnetic resonance (NMR) data were acquired. The NMR experiments required sample clean-up (to remove additives) and long acquisition times (up to 720 min) for 13C NMR. Cleanup also improved the ES results, providing better agreement with the NMR data. However, qualitative and semi-quantitative information was obtainable by ES (but not by NMR) without the cleanup step. Full quantitation of monomer ratios would require suitable standards, but even without such standards the ES measurements provide a rapid (<1 min) means for differentiating these samples (e.g., for process or quality control).