Just when you thought PFAS testing couldn't get more complicated....

There are generally two types of analyses for PFAS: (1) an analysis to detect and quantify the presence of specific PFAS, typically around 40 compounds (and varies lab to lab); and (2) an analysis measuring just the presence of fluorine confirming PFAS is present without identifying the specific one(s). Which one you use depends on whether it is a Prop 65 case – and in some cases you may need to test under both methods for the same product.


Regulatory programs which restrict or evaluate exposure/health risk of specific PFAS, like Proposition 65, use analytical methods that are capable of identifying and quantifying the specific PFAS at issue. This information is needed by the plaintiff to demonstrate exposure to the listed PFAS and defendants need this data to demonstrate the presence of the listed PFAS alleged to be present in the product does not pose a significant risk. There are methods to measure and quantify specific PFAS compounds and there are methods that measure whether fluorine is present. The presence of fluorine means PFAS is present.

Proposition 65 currently lists three PFAS chemicals - perfluorooctanoic acid (PFOA), perfluorooctanoic sulfonate (PFOS), and perfluorononanoic acid (PFNA). While there are two different methods to test for PFAS, only one type measures the specific amounts in the product or food. To defend a Prop 65 claim you need to know the amount of the chemical in the thing tested. There are currently two methods generally available for analysis of these compounds – a method validated by the FDA for PFAS in foods (FDA CC-010.02) and one validated by the EPA for measuring PFAS in water (EPA Method 537). The EPA method was established first and has been adapted by many labs for measuring PFAS in media other than water, and EPA has drafted a method to test outside of water. The FDA method will be applied to foods and, like the EPA method, will be adapted to other media as well. The difference between the two is how the sample is extracted and what solvent is used to do so. Methanol is the solvent typically used for PFAS given its high solubility.


Some non-Prop 65 laws require measuring the presence of PFAS generally and not for the presence of a specific PFAS compound or its concentration. To prove that there is compliance with Prop 65 means knowing the specific amount of the chemical present. Some non-Prop 65 laws require the measurement of "total organic fluorine" (TOF"). All PFAS contain fluorine. Unlike the EPA and FDA methods used in a Prop 65 case that need to be used to calculate the exposure from a specific identified PFAS chemical, TOF does not identify a specific PFAS compound in the product - only that it is present and in what amount. Why is this important to know and why can't you use the more precise methods used in Prop 65? Because California has laws that require (or will require when they go into effect) the measurement of TOF to determine compliance. This includes, for example, laws related to PFAS in food packaging, textiles and cosmetics. In these instances the laws mandate TOF not exceed 100 ppm "total organic fluorine" (TOF). There is more than one way to conceivably measure TOF.

One way to measure TOF is by using an analytical method detecting the presence of fluorine in a sample via an indirect method referred to as Combustion Ion Chromatography (CIC). To simplify the description of the CIC method, the sample is combusted, if fluorine is present it is converted to hydrogen fluoride (HF), the HF is captured in a liquid media, and the liquid media is analyzed using ion chromatography to detect the presence of fluorine. The fluorine is summed, adjusted to account for background, etc., and the adjusted value is used to estimate total organic fluorine present. This is an indirect method.

Another variation on measuring fluorine in a product is EPA draft Method 1621. This process separates absorbable organic fluorine (AOF) in the sample from inorganic fluorine followed by CIC to measure TOF in liquid matrices. For solid matrices, the solid is extracted with a liquid media to remove the inorganic fluorine leaving the extractable organic fluorine (EOF) in the liquid extractant followed by CIC to measure the TOF in the solid matrix. A drawback of this method is that the TOF measured may not correlate with the PFAS present in the sample measured using other methods that identify the specific PFAS compounds present.

Regardless of method used, there may be instances where a product or food has to be tested under multiple methods - for Prop 65 compliance and then for compliance with regulations requiring measurement of TOF.

Finally, there remains some disagreement as to whether there are any validated methods to measure TOF in solid consumer products.


For any PFAS testing there are certain questions to ask a laboratory. Find out whether the lab is accredited and is it accredited for the type of testing and products involved (i.e., food), what is the testing methodology used, and has the lab validated it? Is it a modification of an existing method, and if so has that been validated? A good lab will talk to you about pros and cons of the method it uses and its experience and any challenges that it has faced testing with these methods to date. Given the many unknows and the fact that there is no consensus on which testing is reliable and accurate for PFAS yet, one has to exercise caution and may need to consider multiple labs and methods be used

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.