Total oxidizable precursors assay for PFAS in human serum

Cioni, Lara; Nikiforov, Vladimir; Coêlho, Ana Carolina M. F.; Sandanger, Torkjel M.; Herzke, Dorte

doi:10.1016/j.envint.2022.107656

Cited by 21 publications

(34 citation statements)

References 45 publications

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“… One of the key benefits of the TOP assay is its compatibility with the same analytical instrumentation utilized in targeted analysis, which renders it more accessible to laboratories, as they do not need to invest in additional instrumentation. This feature has facilitated the application of the TOP assay to diverse matrices, including surface waters, soils, sediments, animal tissue, eggs, pesticides, and textiles. − The TOP assay is gaining traction beyond research for its potential utility in site investigations and regulatory assessments. However, no clear guidance is offered for applications of the TOP assay in these different scenarios.…”

Section: Total Oxidizable Precursor (Top) Assay For Environmental App...mentioning

confidence: 99%

Total Oxidizable Precursor (TOP) Assay─Best Practices, Capabilities and Limitations for PFAS Site Investigation and Remediation

Ateia

Chiang²,

Cashman

et al. 2023

Environ. Sci. Technol. Lett.

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The comprehensive characterization of per-and polyfluoroalkyl substances (PFASs) is necessary for the effective assessment and management of risk at contaminated sites. While current analytical methods are capable of quantitatively measuring a number of specific PFASs, they do not provide a complete picture of the thousands of PFASs that are utilized in commercial products and potentially released into the environment. These unmeasured PFASs include many PFAS precursors, which may be converted into related PFAS chemicals through oxidation. The total oxidizable precursor (TOP) assay offers a means of bridging this gap by oxidizing unknown PFAS precursors and intermediates and converting them into stable PFASs with established analytical standards. The application of the TOP assay to samples from PFAScontaminated sites has generated several new insights, but it has also presented various technical challenges for laboratories. Despite the increased number of literature studies that include the TOP assay, there is a critical and growing gap in the application of this method beyond researchers in academia. This article outlines the benefits and challenges of using the TOP assay with aqueous samples for site assessments and suggests ways to address some of its limitations.

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Section: Total Oxidizable Precursor (Top) Assay For Environmental App...mentioning

confidence: 99%

Total Oxidizable Precursor (TOP) Assay─Best Practices, Capabilities and Limitations for PFAS Site Investigation and Remediation

Ateia

Chiang²,

Cashman

et al. 2023

Environ. Sci. Technol. Lett.

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“…For the TOP assay, 150 μL of serum was processed using a previously published protocol. 32 Briefly, samples were spiked with 13 C-PFAA and extracted with ACN. After vortexing, sonication, and centrifugation, the supernatant was collected and split into two portions: one for target analyses before oxidation and one was oxidized for TOP determination.…”

Section: Total Oxidizable Precursor Assaymentioning

confidence: 99%

“…However, it is important to highlight that the TOP assay provides only a lower bound estimate of precursor concentrations since conversion of precursors to PFAA can be incomplete. 32,81 The TOP assay also provided key information on the structure of precursors, namely, minimal length of the perfluorinated carbon chain and presence of sulfur. The UEOF found in pooled serum clearly indicates the need for additional tools to assess previously unidentified fluorinated compounds.…”

Section: Implications and Limitationsmentioning

confidence: 99%

“…The total oxidizable precursor (TOP) assay, in which PFAA concentrations are measured before and after controlled oxidation, offers a promising means for quantifying the total contribution from both known and unknown precursors. While the TOP assay has been used successfully to determine PFAA precursors in environmental samples − and consumer products, − there are few examples of its application to human serum, , and in particular no examples when used in conjunction with an FMB.…”

Section: Introductionmentioning

confidence: 99%

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Fluorine Mass Balance, including Total Fluorine, Extractable Organic Fluorine, Oxidizable Precursors, and Target Per- and Polyfluoroalkyl Substances, in Pooled Human Serum from the Tromsø Population in 1986, 2007, and 2015

Cioni,

Plassmann,

Benskin

et al. 2023

Environ. Sci. Technol.

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Of the thousands of per- and polyfluoroalkyl substances (PFAS) known to exist, only a small fraction (≤1%) are commonly monitored in humans. This discrepancy has led to concerns that human exposure may be underestimated. Here, we address this problem by applying a comprehensive fluorine mass balance (FMB) approach, including total fluorine (TF), extractable organic fluorine (EOF), total oxidizable precursors (TOP), and selected target PFAS, to human serum samples collected over a period of 28 years (1986, 2007, and 2015) in Tromsø, Norway. While concentrations of TF did not change between sampling years, EOF was significantly higher in 1986 compared to 2007 and 2015. The ∑12PFAS concentrations were highest in 2007 compared to 1986 and 2015, and unidentified EOF (UEOF) decreased from 1986 (46%) to 2007 (10%) and then increased in 2015 (37%). While TF and EOF were not influenced by sex, women had higher UEOF compared to men, opposite to target PFAS. This is the first FMB in human serum to include TOP, and it suggests that precursors with >4 perfluorinated carbon atoms make a minor contribution to EOF (0–4%). Additional tools are therefore needed to identify substances contributing to the UEOF in human serum.

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“…The total oxidizable precursor (TOP) assay provides a means of estimating the concentration of a substantial fraction of unknown PFASs in samples, especially in locations where various AFFFs have been used . The TOP assay employs hydroxyl radical ( • OH), a nonselective oxidant, to oxidize most PFASs, otherwise known as precursors, into more readily quantifiable perfluoroalkyl carboxylates (PFCAs). , Polyfluorinated compounds, such as ADONA, that contain an ether group with unsubstituted moiety (–O–CFH–) in the perfluoroalkyl chains can undergo oxidation by the TOP assay into perfluorinated ether carboxylic acids …”

Section: Introductionmentioning

confidence: 99%

Improved Total Oxidizable Precursor Assay for Quantifying Polyfluorinated Compounds Amenable to Oxidative Conversion to Perfluoroalkyl Carboxylic Acids

Tsou,

Antell,

Duan

et al. 2023

ACS EST Water

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Despite the fact that thousands of perfluoroalkyl and polyfluoroalkyl substances (PFASs) are in widespread commercial use, analytical methods capable of quantifying them in environmental samples are available for less than 100 compounds. The total oxidizable precursor (TOP) assay provides a means of quantifying unknown PFASs by oxidizing PFASs into perfluoroalkyl carboxylates (PFCAs), which are readily measured by liquid chromatography−tandem mass spectrometry. To improve the reproducibility of the TOP assay, [ 13 C 8 ] perfluorooctane sulfonamide was added to samples prior to oxidation as an efficiency indicator and its conversion to [ 13 C 8 ] perfluorooctanoic acid was quantified. The recovery of precursors was also improved by including the analysis of ultrashort PFCAs, namely trifluoroacetic acid and perfluoropropyl carboxylic acid, which revealed the presence of ultrashort precursors. A method for distinguishing between branched and linear PFCAs was also integrated into the assay to enhance its ability to differentiate between PFASs produced by electrochemical fluorination and those produced by fluorotelomerization. In addition to its potential application in forensic studies, the improved TOP assay reduces uncertainties associated with incomplete oxidation of precursors or formation of ultrashort PFCAs that are not detected by standard analysis methods.

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Total oxidizable precursors assay for PFAS in human serum

Cited by 21 publications

References 45 publications

Total Oxidizable Precursor (TOP) Assay─Best Practices, Capabilities and Limitations for PFAS Site Investigation and Remediation

Total Oxidizable Precursor (TOP) Assay─Best Practices, Capabilities and Limitations for PFAS Site Investigation and Remediation

Fluorine Mass Balance, including Total Fluorine, Extractable Organic Fluorine, Oxidizable Precursors, and Target Per- and Polyfluoroalkyl Substances, in Pooled Human Serum from the Tromsø Population in 1986, 2007, and 2015

Improved Total Oxidizable Precursor Assay for Quantifying Polyfluorinated Compounds Amenable to Oxidative Conversion to Perfluoroalkyl Carboxylic Acids

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