Per- and Polyfluoroalkyl substances (PFAS) are a class of fluorinated organic compounds known colloquially as “forever chemicals” because of their environmental persistence. A universally accepted PFAS definition does not currently exist. Various organizations, such as the U.S. Environmental Protection Agency (EPA) and the Organisation for Economic Co-operation and Development (OECD), are using different criteria.1
In response to customer requests for PFAS compound coverage in our spectral libraries and specific databases, an updated EPA method was used in the determination2. The most current EPA PFAS substructure query (Figure 1) was used to identify potential PFAS compounds in Wiley's Spectral Libraries. Additional information regarding the current EPA PFAS substructure query can be found at the EPA CompTox Chemicals Dashboard:
https://comptox.epa.gov/dashboard/chemical-lists/PFASSTRUCTV5
Figure 1. In Wiley's KnowItAll software3 (ChemWindow application), the current EPA PFAS substructure query was drawn and searched (SearchIt application) against the KnowItAll reference libraries to identify potential PFAS compounds in each library. The resulting PFAS compound coverage is listed in Table 1 and Table 2.
| Spectral Library Collections | Number of Spectral Records |
| KnowItAll IR Spectral Library | 1,105 |
| KnowItAll Raman Spectral Library | 165 |
| KnowItAll GC-MS Library | 8,350 |
| KnowItAll LC-MS Library* | 7,205 |
| KnowItAll NMR Spectral Library | 14,315 |
| KnowItAll UV-Vis Spectral Library | 25 |
| Wiley SmartSpectra IR Database Collection | 9,080 |
| Wiley SmartSpectra Vapor Phase IR Database Collection | 3,010 |
| Wiley SmartSpectra Raman Database Collection | 3,325 |
| Spectral Libraries – Total | 46,580 |
Table 1. PFAS Compound Coverage in the KnowItAll Spectral Libraries.
*KnowItAll LC-MS library also contains a class-rule based PFAS library.
| Spectral Library Collections | Number of Spectral Records |
| Wiley Registry of Mass Spectral Data 2023 | 7,420 |
| NIST 2023 (GC/MS) | 8,935 |
| NIST 2023 (MS/MS) | 4,155 |
| Spectral Libraries – Total | 20,510 |
Table 2. Additional PFAS Compound Coverage.
In KnowItAll 2026, the most current EPA PFAS substructure query (Version 5) is located at the following file path, in the “Markush Type Structures” database [Record ID #6]: C:\Users\Public\Documents\Wiley\KnowItAll\Samples\Structures\Markush Type Structures
References
1) Williams AJ, Gaines LGT, Grulke CM, Lowe CN, Sinclair GFB, Samano V, Thillainadarajah I, Meyer B, Patlewicz G, and Richard AM (2022). Assembly and curation of lists of per- and polyfluoroalkyl substances (PFAS) to support environmental science research. Frontiers in Environmental Science, 10, 209. doi: 10.3389/fenvs.2022.850019
2) Gaines LGT, Sinclair G, and Williams AJ (2023). A proposed approach to defining per- and polyfluoroalkyl substances (PFAS) based on molecular structure and formula. Integrated Environmental Assessment and Management. doi: 10.1002/ieam.4375
3) KnowItAll Informatics System 2026, Analytical Edition. Copyright © 2001-2026 John Wiley & Sons, Inc. All Rights Reserved.
Acknowledgements
Special thanks to the following individuals for providing additional information regarding PFAS compounds:
- Linda Gaines, Environmental Engineer in the Office of Superfund Remediation and Technology Innovation (OSRTI), Office of Land Emergency Management (OLEM), U.S. Environmental Protection Agency
- Antony Williams, Computational Chemist in the Office of Research & Development, Center for Computational Toxicology & Exposure (CCTE), U.S. Environmental Protection Agency