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Part 4 - Closing the PFAS Mass Balance: The Total Oxidizable Precursor (TOP) Assay

Part 4 - PFAS: Closing the PFAS Mass Balance: The Total Oxidizable Precursor (TOP) Assay (1)

Tuesday, May 7, 2019 & September 24, 2019

About This Webinar:

Current methodologies for the analysis of per and polyfluoroalkyl substances (PFAS) are designed to measure a discrete list of ~20 compounds. There are many additional PFAS compounds that are not determined as discrete compounds by existing analytical methods, including Method 537. Hence, we may be underestimating the PFAS risk potential present in the environment. There is significant pressure from the public, environmental agencies, and others to apply methodologies that more closely measure the full extent of PFAS contamination.

TestAmerica Sacramento implemented the TOP assay as a solution to this complex problem.  The TOP assay rapidly converts polyfluorinated PFAA precursors into PFAAs including PFOA, using a hydroxyl radical-based chemical oxidation method.  The TOP assay replicates what micro-organisms in the environment would achieve after many years.  The TOP assay quantifies the sum of PFAS that could be converted to PFAAs in the environment.  The TOP methodology has revealed that for AFFF-impacted sites, the existing analytical LCMSMS methods are only detecting an estimated 30% to 50% of the total PFAA mass present as PFAA precursors.

In 2006, the United States Environmental Protection Agency (US EPA) announced the PFOA Stewardship Program, to phase out the emissions and the use of long-chain perfluorinated chemicals (PFCs), by December 31st, 2015.  In addition, the US EPA and state agencies have developed health based advisories or screening levels as these chemicals are persistent, bio accumulative and toxic.  The chemistry and analysis of PFASs is unique, interesting and challenging.

In this presentation, we will discuss PFAS generation, formation and environmental release to sampling and analysis.  We will also discuss the current regulatory status of these chemicals.  

Topics the Presentation Will Cover Include:

A Brief PFAS introduction, including:

  • Nomenclature
  • Chemical structure
  • Formation, transport and risk
  • Analytical methodology and current regulatory guidance

In depth explanation of the Total Oxidizable Precursor (TOP) Assay

  • Background
  • What is the TOP assay?
  • How does it work?
  • The TOP assay chemical reaction
  • What do the results mean?
  • What are the limitations of the assay?

Future Concerns

Capabilities and Questions?

A question and answer session will immediately follow the presentation. At the conclusion of each webinar, you will be asked for your feedback and opinions for future webinar topics to be developed by TestAmerica.

May 7, 2019

*This webinar has ended*

September 24, 2019


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PDH Credit:

All webinar attendees will receive a certificate of attendance with PDH Credit issued by TestAmerica. Certificates will be emailed two days following the presentation. Contact your state to determine whether these credits meet the guidelines set forth by your state's board.

The Presenter:

Karla Buechler

PFAS, Explosives and LCMS Support

Corporate Technical Director, TestAmerica

To view a recorded version of this webinar, please contact patricia.mcisaac@testamericainc.com.