Total Organofluorine (TOF & TOP) Test Methods

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TOF & TOP test methods analyze for total organoflourines in a sample. Pace® offers several different methods for different scenarios.

Why Test for TOF & TOP?

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 organoflourines can provide a more complete picture of PFAS contamination to support remediation and control efforts.


Matrices: Ground & Surface Waters, Wastewater, Leachate, Wastewater Sludge & Biosolids, Soil & Other Solids

Compounds: total fluorine content

AOF (Adsorbable organofluorine) is an evolving method for analyzing total organofluorine in a liquid matrix. The EPA is in the process of validating a test method for AOF, and Pace® was selected to support this method development effort. Similar to True-TOF, this method also uses C-IC instrumentation.

EOF (extractable organofluorine) EOF uses an extraction process but can be used with solid matrices like soil and sediment. Like AOF, a modification is required to remove the inorganic fluoride to ensure accuracy of results.


Matrices: Ground & Surface Waters, Wastewater, Leachate, Wastewater Sludge & Biosolids, Soil & Other Solids, AFFF

Compounds: total organofluorine

Developed by Pace®, True-TOF quantifies the total organofluorine in a liquid sample without extraction to a carbon media. Without the need for extraction, True-TOF can be a more reliable test than other methods, such as AOF, because 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 organofluorine 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.

For more details on TOF test methods

EPA Draft Method 1621

Matrices: All Aqueous Matrices

Compounds: total organofluorine (TOF)

EPA Draft Method 1621 is described by the EPA Office of Water 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 organofluorine at the parts-per-billion level in all aqueous matrices. Pace® was chosen to perform the single-lab validation for Draft Method 1621 and will also be participating in the multi-lab validation phase expected to take place summer of 2022. 

TOP Assay

Matrices: Ground & Surface Waters, Wastewater, Leachate, Wastewater Sludge & Biosolids, Soil & Other Solids, AFFF

Compounds: total PFAS, including PFAS precursors

PFAS precursors are a class of PFAS compounds that can degrade to terminal PFAS compounds (i.e., PFAAs) 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 worst-case 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.


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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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We’re on the leading edge of science, working with EPA, DOD, ASTM, and others to develop new methods for analyzing PFAS.