PFAS Sampling in Water and Wastewater using Teledyne ISCO Samplers
According to the Michigan DEQ guidance for PFAS sampling, all sampling equipment can be thoroughly cleansed with either Alconox® or Liquinox® detergents and PFAS-free water both inside and out. Equipment should also be thoroughly rinsed with PFAS-free water before use and arrival at the sampling site. ISCO further recommends installing new, clean silastic tubing (#606700062) for the pump and distributor arm. The suction line tubing should be new, clean food-grade Polyethylene (PE) tubing (St. Gobain: Tygon® HA-1000 #AVT00029, 3/8" ID x 5/8" OD) and outfitted with the ISCO non-PTFE strainer (#605314552). The sampling bottles should be made from PE/PP material (as ISCO ProPak #686700112, also PE bottles: 1L #68210007, 2L #682740026, 3.7L #6067000020 and 500mL wedge #68290002). Alternative Polypropylene (PP) liners are available and should be used inside the bottle caps (Interstate Specialty Products, Sutton, MA). Conventional glass bottles and any sample water contact with Teflon™-like (e.g., PTFE, FEP, PFA or PVDF, to name a few) material should be avoided. Since tubing and bottles can vary from different batch, it is wise to test them for cleanliness and absorbance.
The Michigan DEQ guidance (4.6.2) requires as Field Quality Control Samples, three levels of blank samples: equipment rinse blanks (EB), field blanks (FB) and trip blanks (TB). The chances of false positives are high during PFAS sampling, since PFAS are now ubiquitous in the environment with many possible sources for cross-contamination, e.g., snack-food wrappers and insect repellent, and the low laboratory analysis detection limits, i.e., parts per trillion. Extra care is needed during site visits with sampling equipment.
The equipment rinse blank (EB) could be collected at the lab before leaving for the site using the equipment outfitted with silastic tubing, suction line and strainer. PFAS-free water is sampled by the equipment and collected in a new, clean PE/PP sample bottle. This sample bottle is capped with new, clean PP liner and cap, and kept at the lab for analysis. Since extra time is required in setting-up and breaking down the equipment, the EB could also be performed on site but before installation. An extra PE/PP bottle of PFAS-free water can be brought to the site. The equipment is set-up and used to collect this water in another PE/PP bottle inside the sampler. This sample bottle should be promptly capped using PP liner and returned to the lab after the site visit. Ensure that it is properly labelled.
The field blank (FB) is prepared in the lab with PFAS-free water in a new, clean PE/PP bottle with PP liner but must be treated in every respect like the other samples: travel from the lab to the site, exposure to the site conditions, storage, preservation, return to the lab and all analytical procedures. An extra capped PE/PP bottle of PFAS-free water is brought to the site and installed within the sampler. The sampler equipment is installed at the site. After installing the other empty sample bottles within the sampler, the cap from the FB bottle is removed. Ensure that the sampler is properly programmed so no new water is accidentally introduced to the FB bottle. During the return visit of the samples, the preservative reagent is added to all bottles, including the FB bottle. All bottles are capped with the PP liner and returned to the lab. The FB bottle is treated the same as the rest of the samples in the lab. Ensure that it is properly labelled.
The trip blank (TB) is prepared in the lab with PFAS-free water in a new, clean PE/PP bottle with PP liner and cap. The capped TB bottle, that is properly labelled, is brought to the site during installation and returned to the lab promptly after the installation visit. No preservative is added onsite. Its cap remains tightly on the bottle during the entire site visit.
Vigilance in handling samples and cleanliness will help in ensuring a successful sampling campaign. Clothing, personal care items, plastic containers and bags can be sources of possible contamination. Ensure that all extra items brought to the site are PFAS-free. Finally tubing and bottles should be checked with blanks and fortified blanks to ensure cleanliness and possible absorbance.
REFERENCES
- General PFAS Sampling Guidance (Michigan Department of Environmental Quality, Revised 10/16/2018)
- Per- and Polyfluoroalkyl Substances (PFAS) Sampling Guidelines for (California State Water Quality Control Board: 2020)
