Current PFAS test methods can analyze for roughly 40 compounds. That’s less than 0.1% of the approximately 4,700 CAS-registered compounds classified as PFAS. Testing for total PFAS can provide a more complete picture of PFAS contamination to support remediation, destruction, and control efforts.
AOF measures adsorbable organic fluorine in a liquid matrix. Similar to True-TOF®, this method also uses C-IC instrumentation; however, AOF allows for a lower reporting limit than True-TOF®. For example, AOF can be used as a tool to assess organic fluorine concentrations in AFFF containing waste, which might have a high ppm level content and cause issues with speciated PFAS methods.
The U.S. EPA is in the process of validating a test method for AOF as Draft Method 1621. The EPA Office of Water describes Draft Method 1621 as a “Screening Method for the Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by Combustion Ion Chromatography (CIC).” As drafted, this method can quantify total organic fluorine at the parts-per-billion level in all aqueous matrices. Pace® was chosen to perform the single-lab validation for Draft Method 1621 and is also participating in the multi-lab validation phase that began in the summer of 2022.
EOF uses an extraction process but can be used with solid matrices like soil and sediment. As with AOF, a procedure is required to remove the inorganic fluoride and ensure accuracy of results. EOF is an excellent tool to estimate organic fluorine levels in a wide array of solid sample matrices that might need to be monitored for disposal purposes. This is of upmost importance as the U.S. EPA has proposed to regulate PFOA and PFOS as hazardous substances under CERCLA.
Developed by Pace®, True-TOF® quantifies the total organic fluorine in a liquid sample without extraction to a carbon media. Without the need for extraction, True-TOF® can be deemed a more robust test method as extraction efficiency concerns are not an issue. True-TOF® is also a low volume test that only requires 10 mL of liquid matrix. True-TOF® is one of the methods Pace® uses to analyze for total organic fluorine in aqueous matrices. The technology used for this method is combustion-ion chromatography (C-IC) using a novel system where both the inorganic fluoride and total fluorine can be quantitated, the difference reported as True-TOF®.
Organic fluorine methods can be used as a screening tool for wastewater. To learn more about testing for PFAS in wastewater, watch our on-demand webinar: PFAS Considerations for Wastewater Professionals.
PFAS precursors, both known and unknown, are a class of PFAS compounds that can degrade to terminal PFAS compounds (i.e., perfluoroalkyl acids such as PFHxA ) under the right environmental circumstances. TOP Assay oxidizes PFAS precursors, most of which are compounds not currently measured by targeted techniques, turning them into their terminal PFAS compounds that can then be measured. The increase in PFAS measured after the TOP Assay oxidation relative to pre-oxidation levels is a maximum estimate of the total concentration of PFAS precursors present in a sample. PFAS analysis by TOP Assay is particularly useful in forensic studies designed to identify the source of elevated PFAS levels in all matrices. TOP Assay is a commonly used on complex sample matrices such as leachate, wastewater, biosolids, and AFFF.
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We can test for PFAS in both solid and aqueous matrices, including potable and non-potable waters, soils, and biota.
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