Strategies for the analysis of poly(methacrylic acid) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

We evaluated several aqueous-based sample preparation protocols for the analysis of poly(methacrylic acid) (PMAA) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The sample contained a pentaerythritol tetra(3-mercaptopropionate) end-group, and was characterized in positive and negative ion modes using 2,5-dihydroxybenzoic acid (DHB) and 2,4,6-trihydroxyacetophenone (THAP) matrices. The major series observed were the M + Na species, in positive ion mode, and the M - H species, in negative ion mode. The performance of DHB and THAP matrices was comparable in positive ion mode, but THAP outperformed DHB in negative ion mode. The use of ion-exchange beads (IXB) benefited the analysis, while the addition of sodium acetate (NaOAc) or trifluoroacetic acid (TFA) proved disadvantageous in positive ion mode.