The application of an IR laser working at a wavelength of 3.27 μm, for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and matrix-less laser desorption/ionization of different polymers, has been demonstrated. The ionization/desorption of polyethyleneglycols (PEG) and polymethylmethacrylate (PMMA) could be achieved using matrices commonly used for UV laser desorption of polymers as well as for IR laser desorption of biopolymers and proteins. In addition to these matrix-assisted processes, IR-laser desorption/ionization (LDI) of non-polar waxes could be obtained without additional matrix and silver salts. The MALDI spectra of polymers recorded after UV and IR ionization/desorption have been compared with respect to their peak resolution and the shapes of their molecular mass distributions, whereas the LDI spectra of waxes were compared with earlier results obtained by means of UV-MALDI. In contrast to the commonly used and well-established UV-MALDI of synthetic polymers, it must be mentioned that the resolution of peaks obtained by means of IR-MALDI is almost always much lower.
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Weidner et al. (1998) studied this question.