Discrimination of Polymers by Using Their Characteristic Collision Energy in Tandem Mass Spectrometry

Abstract

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 < R(2) < 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.

Tandem Mass Spectrometric Analysis of a Mixture of Isobars Using the Survival Yield Technique

“…An important point is that at the same molecular ion mass, the SY curve obtained for lithium cationized PTMEG is shifted to much higher excitation voltages compared with the one obtained for PLA. This is in agreement with our recent observation that polyethers do fragment at significantly higher excitation voltages compared with polyesters [19]. + is fragmenting, to finally reach 0 value at high excitation voltages (complete fragmentation of both cationized homopolymers).…”

“…This analysis was performed on another polyether, namely poly(ethylene glycols), and tested on a wide variety of conditions (different instruments, data statistical treatment, experimental conditions …). Moreover, when structurally different compounds are studied, the same linearity is observed but with different rate of increase [19]. Combining these two observations suggests the shift of the SY curves observed for isobars would increase with their mass providing the fragmentation parameters remain independent of the molecular ion mass.…”

“…Using the proposed methodology, they may be easily traced for isobaric contamination even for large mass compounds. These synthetic oligomers are, indeed, known to fragment at much higher energies than biological compounds [15,19,22] that allow for using the methodology presented in this work. Similarly, polyethers are extensively used in packaging and must thus be tracked in, e.g., foodstuff, for possible contamination.…”

“…Using this definition, one may record and plot the value of this ratio as a function of the excitation voltage: this leads to the SY curve. This technique has already been used in fundamental studies [15][16][17][18], but also to discriminate molecular ions according to their structures [19][20][21]. When doing so in the same experimental conditions for both homopolymers separately and for a mixture of 5:1 (PLA/PTMEG), one obtains the curves displayed in Figure 2.…”

Electrospray Ionization Tandem Mass Spectrometry of Ammonium Cationized Polyethers

“…Comparison of the curves is done using the characteristic point of 50% survival yield. The rationale for use of this reference point is described in previous work [34]. The ranking based on this point is: (AD + H) + (40.1 eV) 9 C 16 Me 2 NH + (35.7 eV) 9 C 16 Me 3 N + (21.8 eV) 9 C 16 Py + (18.5 eV) 9 Bu 3 NH + (16.4 eV).…”