Next, the product ion spectrum of TMe/E (Figure 3B), which has one end-group that is different from E/E, showed unique ions that were labeled with red arrows. First, the E/E product ion spectrum (Figure 3A), which has the same end-group structure at both ends, was analyzed, and the product ions highlighted with blue arrows were used to support the estimated structure. The estimated structure (n=5) and the fragmentation position are shown in each product ion spectrum. The product ion spectra showed common ions as well as several mass spectral peaks with separation intervals of 192u, which all suggest that these ions have similar structures. Figures 3 and 4 show the product ion spectra for these ions. Three oligomers generated by on-plate alkaline degradation were selected for TOF-TOF analysis: TMe/E ( m/z 1015), E/E ( m/z 1045) and TMe/E(diE) ( m/z 1059). The KMD plots of PET before(A) and after(B) on-plate alkaline degradation (base unit C 10H 8O 4:192.04, x=198) The proposed structures for peaks 1-3 are shown in Figure 1C.įigure 2. However, after the on-plate decomposition, there were 10 different series observed in the sample. Before the on-plate alkaline degradation, there were two characteristic cyclic oligomer series observed in the mass spectrum. Spot the THAP HFIP/THF solution on the dried sample spot.įigure 1 shows the mass spectra before and after applying the on-plate alkaline degradation method.After on-plate decomposition, the sample spot was desalted with purified water.Spot and dry the NaOH solution on the sample spot.Spot the sample solution on the target plate.The high resolution mass spectra were measured by using SpiralTOF positive ion mode, and HE-CID measurements were performed in TOF-TOF positive ion mode. Sodium hydroxide (NaOH) 10 mg/ml methanol solution was used for on-plate alkaline degradation. The matrix compound 2,4,6-trihydroxyacetophenone (THAP) was dissolved in HFIP/tetrahydrofuran (THF) at a concentration of 10 mg/ml. PET (film) was dissolved in hexafluoro-2-propanol (HFIP) solution at a concentration of 10 mg/ml. The SpiralTOF TM-plus uses an ultra-high resolution TOF for MS1 which allows monoisotopic precursor selection and a reflectron TOF for MS2 to analyze the product ion spectra produced from high energy collisional induced dissociation (HE-CID). In this report, we investigated the structural analysis of the polyethylene-terephthalate (PET) polymer exposed to the on-plate alkaline degradation method by using the JMS-S3000 "SpiralTOF TM-plus" with TOF-TOF option. This degradation into oligomers is not only advantageous for accurate mass analysis but also for structural analysis by using tandem time-of-flight mass spectrometry (TOF-TOF). One way to address this is to use an “on-plate alkaline degradation” method that was previously published in which high molecular weight polyester or polycarbonate are partially hydrolyzed by an alkaline reagent to form smaller oligomers that can then be analyzed by high-resolution MALDI-TOFMS. For example, as the polymer molecular weight increases, the ionization efficiency, detection sensitivity, and ratio of monoisotopic ions used for accurate mass analysis all decrease. However, there are limitations to doing accurate mass analysis of high molecular weight polymers. This technique, when combined with a high-resolution time-of-flight mass spectrometer, can be used to identify differences in monomer, polymer end groups, and their molecular weight distributions. Matrix assisted laser desorption/ionization (MALDI) mass spectrometry is a powerful tool for the analysis of synthetic polymers.
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