A How-To for Sampling Water & Wastewater to Detect PFAS
Per- and polyfluoroalkyl substances (PFAS) can be detected in trace amounts in water and wastewater, but obtaining an accurate assessment is a challenge due to the ubiquitous nature of the chemicals. Exacting steps must be taken before, during and after samples are obtained to ensure they are not compromised.
As experts in water and wastewater sampling and flowrate measurement for more than 60 years, Teledyne ISCO is uniquely qualified to assist in determining and implementing best practices that take much of the guesswork, wasted time, unnecessary expense and inaccurate analysis due to compromised samples out of the equation. Following is a high-level view of industry standards and best practices. For more detailed information specific to your application, feel free to contact our Water Product Support team at firstname.lastname@example.org or in the United States, toll-free at 866-209-6174.
It is important to note that this is a rapidly evolving science, and these pages will be updated as the subject evolves.
Equipment Choices/Material Selection
PFAS sampling is conducted in much the same way as any sampling project; however, extreme care must be taken before, during and after collection to maintain the integrity of the samples. Due to the extreme prevalence of PFAS in our environments and the extremely small quantitative measurements (0.02 ppt) in the EPA guidelines, the potential for cross-contamination is significant. Therefore, far greater care is required to avoid compromising the quality of the collected sample. For example, it is recommended to wear powderless nitrile gloves when working with and around the sampling field.
You must consider not only the materials that will come into direct contact with the sample, but also those materials that will be present in a wide swath of the sample collection area — including those worn and used by the sample technicians. Anecdotally, one entity instructs field personnel to not wash or shampoo the day before they are deploying equipment or collecting PFAS samples due to the cross-contamination potential from soaps, toiletries and hair care products. Again, keep in mind that with PFAS, we are looking for detection in the parts per trillion range, so the potential for significant cross-contamination is very real.
Sources of contamination
Avoid the following before and during sampling or while at the sampling site. While not an exhaustive list, these points again demonstrate the prevalence of PFAS and the care that must be taken.
Please note: PPE could contain PFAS. However, never compromise safety for the sake of eliminating PFAS material. If there is no equivalent PFAS-free option available, document the use of such and use a blank sample to establish a baseline presence of PFAS with the equipment and the exposure potential.
- Personal sources of contamination: soaps, shampoos, insect repellants, sunscreen, moisturizing lotion, cosmetics, some toothpastes
- Clothing that was washed using fabric softeners
- Clothing and textiles marked stain-resistant or waterproof, including raincoats and footwear, rugs and furniture
- Fast food containers/packaging, food or drink in sealed packages (e.g., juice boxes)
- Materials that are NOT in direct contact with the sample but should be avoided include but are not limited to: GPS receivers, notebooks, clipboards, etc. they could have PFAS on their surfaces and become a source of contamination!
Materials to use or avoid in sampler parts
At the top of the list of materials that must be avoided, DO NOT USE PTFE or FEP tubing or any tubing that contains fluoride for suction line or any part of the sampler equipment. Generally speaking, high-density polyethylene (HDPE) sample collection bottles should be used. Low-density polyethylene (LDPE) that has NOT been verified to be PFAS free should NOT be used. Sample collection bottles should be used sparingly for PFAS sampling and then discarded due to the minute trace amounts under consideration.
- Strainer: stainless steel or stainless steel/HDPE
- Tubing coupler and bulkhead fitting: stainless steel
- Suction line: vinyl
- Pump tubing: silicone (See the Teledyne ISCO poster: PFAS Applications-Study on Tubing)
- Collection bottles: HDPE or polypropylene (PP)
- Natural Ice from verified PFAS-free water
Materials to avoid or use with caution
- LDPE (unless tested and verified to be PFAS free)
- Glass (unless tested and verified to be PFAS free). Samples should not be stored in glass for an extended period, as it can absorb PFAS over time and contribute to cross-contamination. Limit the re-use of glass for this reason.
- Teflon or related materials
- Items or materials containing any fluoropolymer
- Sampling equipment used for PFAS sampling should be dedicated to and ONLY used for PFAS sampling. With the trace amounts of PFAS we are looking for, we don't want to have cross-contamination from the equipment used for other purposes.
- Decontamination is a MUST due to the sensitive nature and cross-contamination threat. This is often accomplished with a thorough rinse with known PFAS-free water being run through the sample lines.
- It is recommended that you communicate with your analytical laboratory and appropriate regulatory agency for their specific decontamination recommendations.