关键词: 热裂解, 气相色谱-高分辨质谱联用, 裂解机理, 纤维数据库, 微纤维鉴别

Abstract: Traditional fiber analysis methods are limited by drawbacks such as matrix interference, signal overlap and low sensitivity, which makes it difficult to accurately identify fibers in complex matrices. Pyrolysis-gas chromatography/high-resolution mass spectrometry (Py-GC/HRMS) coupling technology is an efficient analytical technique applicable to various sample forms, requiring low sample amounts and generally eliminating the need for cumbersome pretreatment. Meanwhile, relying on the ultra-high sensitivity of high-resolution mass spectrometry, Py-GC/HRMS can effectively resolve signals from complex components, significantly enhancing the accuracy of identifying fiber characteristic substances. It is thus an ideal method for fiber analysis in complex matrices. However, the existing Py-GC/HRMS fiber analysis databases are incomplete, which hinders the application of Py-GC/HRMS technology in fiber analysis to a certain extent. Therefore, this study investigated the pyrolysis behavior of different types of fibers and established a Py-GC/HRMS analysis database to successfully identify microfibers in the filter materials filtered by washing machine filters. The results showed that vinyl benzoate, ε-caprolactam, cyclopentanone, 1-decene, 2,4-dimethyl-1-heptene, 1,3,5-triphenyl-5-hexene, 1,3,5-tricyanohexane and 1-methylnaphthalene served as characteristic pyrolysis products for identifying polyethylene terephthalate (PET), polyamide 6 (PA6), polyadiohexylenediamine 66 (PA66), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyacrylonitrile (PAN) and polyvinyl chloride (PVC) respectively. The Py-GC/HRMS technology could not directly identify the four types of cellulose fibers (cotton, flax, viscose and tencel). However, levoglucosan could be used as a preliminary characteristic pyrolysis product for identifying cellulose fibers. Indole served as a preliminary characteristic pyrolysis product for identifying protein fibers. In addition, carbonyl sulfide was a unique pyrolysis product of cashmere and wool, aminomethanesulfonic acid was only found in the pyrolysis of duck and goose down, while dimethylamine was exclusively produced by the pyrolysis of silk. In five different samples of filter materials filtered by washing machine filters, PET, PA6, PA66, PAN, cellulose and protein fibers were detected, indicating that washing machine filters could effectively intercept filamentous synthetic fibers shedding during the washing process, thereby reducing the pollution of microplastic fibers in the aquatic environment. Moreover, the presence of PS, ABS and indigo dye was also detected by Py-GC/HRMS, demonstrating that this technology is not only an effective tool for fiber identification in complex matrices but can also be utilized to analyze trace amounts of microplastics and dyes in the environment. This work investigated the pyrolysis behavior of fibers and established a fiber analysis database for identifying microfibers captured by washing machine filters, with the aim of evaluating the fiber release mechanism during fabric washing processes. It provides new insights into the application of Py-GC/HRMS technology and offers valuable methodologies and pivotal reference data for the study of microfibers.

Key words: pyrolysis gas, chromatography-high resolution mass spectrometry, pyrolysis mechanism, fiber database, identification of microfibers