TOP Assay

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Short description: Laboratory analysis method

The TOP Assay (Total Oxidizable Precursor Assay) is a laboratory method developed in 2012[1] that oxidatively converts (unknown) precursor compounds of perfluorocarboxylic acids (PFCAs) into the latter. This makes quantification possible. Potassium peroxodisulfate is used. This sum parameter can be used to determine the concentration of precursor compounds present by comparing the sample before and after the application of the TOP Assay.[2]

Example of oxidation of polyfluorinated compounds (6:2 FTOH, 6:2 FTS, 6:2 FTAB, 6:2 diPAP) using the TOP Assay to form PFCAs

Application

This method is used, for example, in the analysis of fire-fighting foams (aqueous film forming foam), textiles or water samples.[3][4] Blood serum can also be analyzed in this way.[5]

Neutral, anionic and cationic precursor compounds may be distinguished using an extension of the method published in 2025.[6]

In addition to fluorotelomer compounds, hydrogen-substituted perfluorosulfonic acids (Hn-PFSAs), for example, can also be oxidized using the TOP Assay. Saturated and unsaturated perfluorosulfonic acids as well as perfluoroalkyl ether sulfonic acids, on the other hand, are stable.[7]

Further reading

References

  1. ↑ Houtz, Erika F.; Sedlak, David L. (2012-09-04). "Oxidative Conversion as a Means of Detecting Precursors to Perfluoroalkyl Acids in Urban Runoff" (in en). Environmental Science & Technology 46 (17): 9342–9349. doi:10.1021/es302274g. ISSN 0013-936X. PMID 22900587. Bibcode: 2012EnST...46.9342H. https://pubs.acs.org/doi/10.1021/es302274g. 
  2. ↑ Göckener, Bernd; Fliedner, Annette; Rüdel, Heinz; Fettig, Ina; Koschorreck, Jan (August 2021). "Exploring unknown per- and polyfluoroalkyl substances in the German environment – The total oxidizable precursor assay as helpful tool in research and regulation". Science of the Total Environment 782. doi:10.1016/j.scitotenv.2021.146825. ISSN 0048-9697. PMID 33838381. Bibcode: 2021ScTEn.78246825G. 
  3. ↑ Al Amin, Md; Luo, Yunlong; Nolan, Annette; Robinson, Fiona; Niu, Junfeng; Warner, Scott; Liu, Yanju; Dharmarajan, Raja et al. (December 2021). "Total oxidisable precursor assay towards selective detection of PFAS in AFFF". Journal of Cleaner Production 328. doi:10.1016/j.jclepro.2021.129568. ISSN 0959-6526. Bibcode: 2021JCPro.32829568A. 
  4. ↑ Ignacio, Ma Cristine Concepcion D.; Curtzwiler, Greg W.; Early, Mark R.; Updegraff, Katie M.; Vorst, Keith L. (February 2023). "Ion Selective Electrode (ISE) Method for Determination of Total Fluorine and Total Organic Fluorine in Packaging Substrates" (in en). Methods and Protocols 6 (1): 10. doi:10.3390/mps6010010. ISSN 2409-9279. PMID 36827497. 
  5. ↑ Cioni, Lara; Nikiforov, Vladimir; Coêlho, Ana Carolina M.F.; Sandanger, Torkjel M.; Herzke, Dorte (December 2022). "Total oxidizable precursors assay for PFAS in human serum". Environment International 170. doi:10.1016/j.envint.2022.107656. ISSN 0160-4120. PMID 36436462. Bibcode: 2022EnInt.17007656C. 
  6. ↑ Antell, Edmund H.; Yi, Shan; Olivares, Christopher I.; Chaudhuri, Shreya; Ruyle, Bridger J.; Alvarez-Cohen, Lisa; Sedlak, David L. (2025-02-13). "Selective Quantification of Charged and Neutral Polyfluoroalkyl Substances Using the Total Oxidizable Precursor (TOP) Assay". Environmental Science & Technology. doi:10.1021/acs.est.4c13837. 
  7. ↑ Zweigle, Jonathan; Bugsel, Boris; Röhler, Klaus; Haluska, Alexander Arthur; Zwiener, Christian (2023-04-25). "PFAS-Contaminated Soil Site in Germany: Nontarget Screening before and after Direct TOP Assay by Kendrick Mass Defect and FindPFΔS" (in en). Environmental Science & Technology 57 (16): 6647–6655. doi:10.1021/acs.est.2c07969. ISSN 0013-936X. PMID 37058300. Bibcode: 2023EnST...57.6647Z. https://pubs.acs.org/doi/10.1021/acs.est.2c07969. 



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