Since the USEPA’s October 2021 announcement of their PFAS Strategic Roadmap, there has been an almost constant stream of news, information and developments on PFAS, including the methods used to identify, measure and quantify these compounds.

In general, the most prominent PFAS detection methods are solid-phase extraction (SPE), liquid chromatography with tandem mass spectrometry (LC-MS/MS). These methods are proven and reliable for targeted quantification, but are complicated processes that are relatively time-consuming, can only identify limited numbers of PFAS compounds and fail to determine a complete extent of PFAS contamination.  And given the steady increase in the numbers of untargeted compounds, these standard methods aren’t enough to meet the growing PFAS monitoring demands.

Introducing AOF-CIC

Total Organic Fluorine Analysis using Combustion Ion Chromatography is a precise and automated method to determine adsorbable organic fluorine in water samples, providing a complementary technology to targeted methods to help determine a broader more accurate level of PFAS and organofluorine contamination.

Using an automated sample preparation unit, up to 100 mL of aqueous sample is passed across two AOF charcoal tubes connected in series.  After the sample is loaded, the charcoal tubes are flushed with a sodium nitrate solution to remove inorganic fluoride.  After the charcoal tubes are flushed and the inorganic fluoride is removed, the contents of both AOF charcoal tubes are emptied into a single ceramic boat and analyzed using combustion ion chromatography.

This method provides a fast and accurate alternative to the existing standard methods by delivering greater coverage of concentration estimates for PFAS and organofluorine compounds. CIC-TOF is also an ideal complementary technique – with its simpler and more cost-effective method, it is a great pre-screening tool to identify samples which potentially contain additional compounds that were not included in the targeted analysis methods.

What are some ideal applications and Strengths of AOF-CIC?

In addition to general testing, AOF-CIC is advantageous for:

  • Broader PFAS and organofluorine contamination assessment
  • Liability risk assessments – better estimate of true PFAS impact
  • Quickly identifying priority areas that require further evaluation

AOF-CIC’s benefits include:

  • Increased accuracy of total PFAS in a sample
  • Increased accuracy in calculation of remediation costs and processes
  • Reduction in testing costs

USEPA Draft Method 1621

As if these benefits and uses for AOF-CIC aren’t enough, in April 2022 the USEPA published Draft Method 1621 “Screening Method for the Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by Combustion Ion Chromatography (CIC),” a single-laboratory validated method to screen for organofluorines (which are rarely naturally found) in wastewater. The most common sources of organofluorines are PFAS and non-PFAS fluorinated compounds such as pesticides and pharmaceuticals.

This new draft method has completed single-laboratory validation, and multi-laboratory validation is planned for Summer 2022. The EPA will use the results of the validation studies to finalize this method and add formal performance criteria. At this time, the EPA is encouraging interested organizations to review and use the method, under the advisement that it is subject to change and is not nationally required for CWA compliance monitoring until it has been promulgated through rulemaking.

Does AOF-CIC Need to be a part of my PFAS Monitoring Strategy?

AOF-CIC is just another piece of a larger PFAS strategy and a perfect compliment to existing standard testing methods.  But its benefits make it an attractive addition to your planning, and with a price point that is lower than most other testing methods, and a speed and broad accuracy level, it’s worth consideration.

Additional Resources

USEPA Draft Method 1621, Screening Method for the Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by Combustion Ion Chromatography (CIC)

Report on Single-laboratory Validation of Clean Water Act Method 1621 for Adsorbable Organic Fluoride (AOF)

For more information on PFAS monitoring, AOF-CIC or any and all of the methods covered here please contact us.

Mike Allen

VP, Technical

Mike Allen is Vice President, Technical at Enthalpy Analytical. Over the span of his 30-year career, Mike has spent time in various key leadership roles of the analytical laboratory business including new lab start up, operations management, method development validation and troubleshooting, business development, strategic planning, acquisition and integrations.


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