PFAS Sampling Protocol

PFAS Sampling Protocol: Understanding Protocols for Effective Detection and Management

Introduction

Per- and polyfluoroalkyl substances (PFAS) have emerged as a significant environmental concern because of their persistence and potential health risks. With enforceable drinking water limits now measured in parts per trillion, the reliability of PFAS data depends heavily on how samples are collected. At these concentrations, a contaminated glove, the wrong sample bottle, or a waterproof field notebook can introduce more PFAS than the sample itself contains. This article covers the principles and practices of PFAS sampling across water, soil, and other media, with a focus on the precautions that distinguish PFAS sampling from conventional environmental sampling.

Understanding PFAS and Its Implications

What Are PFAS?

PFAS are a large group of synthetic chemicals containing multiple carbon-fluorine bonds, used in non-stick cookware, water-repellent clothing, food packaging, firefighting foam, and many industrial processes.

  1. Environmental Persistence: PFAS are called “forever chemicals” because of their resistance to degradation, which has resulted in widespread contamination of water supplies.

  2. Health Concerns: Exposure to certain PFAS has been linked to liver effects, developmental effects, immune suppression, and increased risk of certain cancers.

  3. Ubiquity: The same properties that make PFAS useful make them common in everyday materials — including many used in field work. This is the central challenge for sampling.

Overview of PFAS Regulations

Current Regulatory Landscape

EPA issued drinking water health advisories for several PFAS in 2022, followed in April 2024 by a final regulation setting enforceable maximum contaminant levels, including 4.0 parts per trillion each for PFOA and PFOS. In May 2026, EPA proposed retaining the PFOA and PFOS limits with an optional compliance extension to 2031 and rescinding the limits for four other PFAS; as of September 2026 those remain proposals. Many states maintain their own PFAS standards for drinking water, groundwater, and soil, and state programs often specify sampling requirements of their own.

Why the Regulatory Level Matters for Sampling

A 4 ppt limit means that contamination introduced at the level of a few parts per trillion can change a compliance determination. Sampling precautions that would be excessive for most contaminants are necessary for PFAS.

Importance of Proper Sampling Protocol

Purpose of Sampling

Sampling serves several purposes:

  • Compliance Monitoring: Demonstrating that drinking water meets regulatory limits.

  • Site Characterization: Defining the extent and source of contamination at impacted sites.

  • Treatment Performance: Tracking removal across treatment systems and detecting breakthrough.

  • Public Health Protection: Providing reliable data on which decisions affecting communities are based.

Common Sampling Challenges

  • Cross-Contamination: PFAS are present in many field materials, clothing, and personal care products, and contamination can easily occur during sampling.

  • False Positives and Negatives: Contamination produces false positives; sorption of PFAS onto certain container materials can reduce measured concentrations.

  • Representativeness: Sampling design must capture conditions that reflect the source being characterized.

Key Elements of PFAS Sampling Protocol

Sampling Locations and Techniques

Choosing representative sampling locations is vital. Common approaches include:

  • Grab sampling, which is standard for drinking water compliance.

  • Composite sampling for broader assessments where permitted by the governing method or program.

Sampling Equipment and Materials

This is the most important element of PFAS sampling protocol. Fluoropolymers must be avoided. PTFE — sold under trade names including Teflon — is itself a PFAS material and is one of the most common sources of sample contamination. It must never be used for sample containers, tubing, bailers, augers, or cap liners.

Acceptable and commonly specified materials include:

  • High-density polyethylene (HDPE) or polypropylene sample containers with unlined polypropylene caps, as specified by the analytical method. Drinking water methods EPA 533 and 537.1 specify polypropylene bottles.

  • Silicone or HDPE tubing for pumps.

  • Stainless steel for augers, trowels, and other soil sampling tools.

  • Nitrile gloves, changed frequently.

Materials commonly prohibited or restricted during PFAS sampling include:

  • PTFE or other fluoropolymer equipment, tubing, and cap liners

  • Waterproof or stain-resistant clothing, including many rain jackets and treated work wear

  • Waterproof field notebooks and some adhesive notes

  • Aluminum foil and certain food packaging

  • Sunscreens, insect repellents, and cosmetics unless verified PFAS-free

  • Chemical ice packs and some plastic sheeting

Field teams should wash hands before sampling, avoid handling food on site, and document any potential contamination sources present.

Sample Preservation and Holding Times

Preservation follows the analytical method. Drinking water samples for EPA Method 537.1 are preserved with Trizma, and those for EPA Method 533 with ammonium acetate; both preservatives remove free chlorine. Samples must be chilled promptly, shipped cold with regular ice rather than chemical ice packs, and delivered within the method’s holding time.

Field Quality Control

Field quality control samples are how contamination is detected when it happens:

  • Field reagent blanks: PFAS-free water carried to the site and exposed to field conditions, required by drinking water methods.

  • Equipment blanks: PFAS-free water passed through decontaminated sampling equipment.

  • Field duplicates: Replicate samples demonstrating precision.

Chain of Custody

A detailed chain of custody demonstrates sample integrity. Documentation must record collection times, personnel, sample identifiers, preservation, and every transfer between custodians.

Field Sampling Procedures

Drinking Water Sampling

  1. Remove aerators and screens from the sampling tap.

  2. Flush the line until water temperature stabilizes, as specified by the program.

  3. Fill bottles directly from the tap without rinsing, leaving any preservative in place.

  4. Open and handle the field reagent blank at the same location during sampling.

Groundwater Sampling

  1. Select representative wells, including source areas and background locations.

  2. Purge before sampling to obtain water representative of the aquifer rather than stagnant well-casing water.

  3. Control flow rates, using low-flow techniques where specified, to minimize turbidity and disturbance.

  4. Use dedicated or properly decontaminated equipment with PFAS-free components, collecting equipment blanks where equipment is reused.

Surface Water Sampling

  • Sample at locations and times that reflect the conditions being characterized, including wet and dry weather where relevant.

  • Be aware that PFAS concentrate at the air-water interface and in surface foam, so sampling depth and the presence of foam affect results.

Soil Sampling

  1. Incremental Sampling: Collecting many increments across a decision unit provides a representative average concentration.

  2. Appropriate Equipment: Use stainless steel augers and tools, never PTFE, with decontamination between locations.

Soil investigations raise distinct questions around leaching potential and background levels, covered in detail in our guide to PFAS soil testing.

Air Sampling

Air sampling for PFAS, typically associated with stack emissions or thermal treatment facilities, uses specialized sampling trains and methods and is generally performed by specialist contractors.

Laboratory Analysis of PFAS Samples

Analytical Techniques

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the standard technique for PFAS analysis. For drinking water, EPA Methods 533 and 537.1 are approved; other matrices require methods validated for those media.

Laboratory Quality Control

  • Calibration Standards: Instruments calibrated with known standards.

  • Laboratory Blanks: Detect contamination introduced in the laboratory.

  • Labeled Standards: Isotopically labeled compounds that monitor and correct for recovery.

Interpreting Laboratory Results

  • Review blanks first: Detections in field or equipment blanks call the associated sample results into question.

  • Compare with applicable standards: Federal and state limits differ, and the relevant standard depends on the medium and program.

  • Look at trends: Longitudinal data is more informative than single results, particularly near regulatory limits.

Best Practices for Implementing PFAS Sampling Protocol

Training Personnel

Sampling staff need specific training in PFAS precautions, which differ markedly from routine sampling practice. Written procedures and pre-sampling checklists reduce reliance on memory.

Coordinating with the Laboratory

Obtain bottles, preservatives, and blank water from the laboratory performing the analysis, and confirm method, holding times, and shipping arrangements before sampling.

Community Engagement

Where sampling affects communities, transparency about what is being sampled, why, and when results will be shared builds trust and cooperation.

Conclusion

At parts-per-trillion concentrations, PFAS data is only as reliable as the sampling behind it. The essentials are consistent across media: avoid fluoropolymer materials entirely, control personal and field sources of contamination, follow the analytical method’s container and preservation requirements, and collect field blanks that demonstrate the sample was not contaminated. Getting these right is what makes the difference between data that supports sound decisions and data that has to be collected again.