Matrix-assisted laser desorption ionisation time-of-flight mass spectrometry of synthetic polyesters

Abstract We report the analysis of aliphatic and aromatic polyesters by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF-MS) using 2,5-dihydroxybenzoic acid and t -3-indoleacrylic acid as matrices. Broad asymmetrical distributions of linear oligomer related peaks (protonated and cationised molecules) were observed with both matrices. Peaks corresponding to cyclic oligomers were observed for the aliphatic polyester. The oligomer molecular weight distribution derived from the MALDI spectra exhibits a certain variability with both laser fluence and matrix material. This effect probably originates from different solubilities of the various oligomers. In addition, for those polycondensates which are characterised by a very broad distribution with a tail in the high mass range, a discrimination against the higher mass oligomers is likely to exist; the agreement between the average molecular weights determined by MALDI and size exclusion chromatography is not as good as for poly(ethylene glycol) or poly(methyl methacrylate).