Electrospray ionization with high-resolution time-of-flight mass spectrometry (ESI HR TOF MS) was evaluated as a method for polymer molecular weight (MW) distribution determination. The ESI feature of multiply charged ion formation allowed for a successful ionization of high and low MW polymer species. An assessment of MW distribution was performed using the subsequent mass spectrum deconvolution.<br/>Unlike size exclusion chromatography (SEC), which is frequently used for polymer analysis, the developed ESI HR MS method allows for determining the polymer repeating unit and the end group structure for regular polymers. The method does not require calibration standards, which is known to be the main limitation of SEC due to the lack of representative standards. Formation of multiply charges ions results in a less pronounced suppression of ionization of high MW species compared to matrix-assisted laser desorption/ionization (MALDI) MS. Therefore a more balanced polymer mass spectrum is recorded when ESI is employed.<br/>The ESI HR TOF MS method was applied to elucidate the MW of synthetic polymers, e.g., polyethylene glycol, polypropylene glycol and a copolymer of styrene oxide and maleic anhydride. We also evaluated ESI HR TOF MS as a method for lignin analysis via direct infusion targeting the simultaneous detection of low and high MW species. The effect of various ionization conditions on ion formation, including a broad range of electrolytes, was investigated using a range of mono-, di- and triarene lignin model compounds as well as intact lignin. For the first time we have shown an effective ionization of intact lignin in the positive ionization mode with formic acid as an optimal electrolyte resulting in formation of multiply charged species. The presence of multiply charged lignin ions was confirmed with ESI ion mobility HR Q-TOF MS. For both synthetic polymers and lignin, the obtained MW values were in good agreement with those determined by SEC.

Effective characterization of oligomers and polymers by electrospray ionization with high-resolution mass spectrometry: New tool for lignomics

255th National Meeting (2018)

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