Discrimination of polymers by using their characteristic collision energy in tandem mass spectrometry

The characteristic collision energy to obtain 50% fragmentation, expressed as the characteristic collision voltage (CCV), was used as a tool to discriminate different classes of polymers. The CCV value of different polymers was determined in a quadrupole ion trap mass spectrometer. Good linear correlation (0.980 < R2 < 0.999) between the CCV values and precursor ion mass was found for all polymers studied. The position of the various linear trend lines varied among the various polymers, which allowed their grouping based on the respective CCV values. The collision energy necessary to drive fragmentation was decreasing in the order of polyethers > polymethacrylates > polyesters > polysaccharides. This suggests that polysaccharides fragment most easily (low CCVs), while polyethers require the highest collision energy among the polymers studied. The effect of end group on the CCV was also studied, showing a minor influence in most cases. In addition, the applicability of CCV as discriminator was studied for a mixture of (1) polylactic acid (PLA), (2) poly(tetramethylene glycol) (PTMEG), and (3) PLA-block-PTMEG-block-PLA block copolymer. Differences between the CCV values of four nominally isobaric polymers (of which two were copolymers and two were homopolymers) were observed. These results demonstrate that the insertion of a “weak” link into a polymer chain significantly affects the energy required for fragmentation.