Identification\nof Omitted Pollutants in Environmental\nWater via In Situ Thin-Film Microextraction

Sample preparation is an inevitable step in the screening\nworkflow\nfor the identification of unknown pollutants in the aquatic environment.\nHowever, the possible loss of pollutants during sample preparation\nhas aroused serious concern but remains not effectively resolved.\nThis study shows that high-risk pollutants omitted in solid-phase\nextraction (SPE) can be identified via in situ thin-film microextraction\n(TFME) coupled with high-resolution mass spectrometry. It was observed\nthat a total of 541 features showed higher mass spectrometry signal\nintensity by using in situ TFME in comparison with SPE. Subsequently,\n28 compounds were identified from the features with higher intensity\nby comparing the recorded tandem mass spectra with the online database\nand validating with standards. Notably, six out of these compounds\nwere completely omitted using SPE, including a dye, drug, and industrial\nproduct. It was confirmed that the lower extraction efficiencies of\nSPE were attributed to the limited sample volumes, the losses of compounds\nduring sample transportation and storage, and the entrapment of compounds\nin SPE columns. This study demonstrates that in situ TFME should be\nused as a supplementary technique to SPE for extending the coverage\nof pollutants in the screening workflows.