PFAS Sampling Best Practices - A Practical Field Guide

Note: This guide is compiled from EPA, ITRC, and DOD published sampling guidance documents. Field procedures for PFAS are evolving rapidly as analytical methods improve and regulatory requirements change. Always confirm current sampling requirements with your analytical laboratory and applicable regulatory program before mobilizing to the field. If you spot an error or outdated procedure, contact us.

Why PFAS Sampling Is Different

If you’ve been doing environmental sampling for years and have never collected PFAS samples before, the most important thing to understand is this: almost everything you normally bring to the field can contaminate your samples.

PFAS compounds are everywhere - in waterproof clothing, food wrappers, cosmetics, sunscreen, insect repellent, and most critically, in the PTFE (Teflon) components that are standard in groundwater sampling equipment. At the parts-per-trillion detection limits required by current regulations, even trace contamination from your equipment or clothing will produce false positives or elevated results.

This isn’t theoretical. Entire sampling events have been invalidated because someone wore a Gore-Tex jacket in the field or used standard PTFE-lined tubing. The cost of resample mobilization far exceeds the cost of getting it right the first time.

Equipment Requirements

What You Cannot Use

These items contain PFAS or PTFE and will contaminate your samples:

• PTFE (Teflon) tubing, tape, or fittings - this is the single most common source of contamination
• PTFE-lined sample containers - standard VOA vials and many glass bottles have PTFE-lined caps
• Viton O-rings and gaskets - commonly found in pump assemblies
• LDPE (low-density polyethylene) bottles - use HDPE instead
• Aluminum foil - often treated with PFAS coatings
• Teflon plumber’s tape - sometimes used to seal well fittings
• Sharpie markers on sample containers (use labels or PFAS-free markers)
• Standard field notebooks with waterproof/water-resistant paper (e.g., Rite in the Rain)
• Post-it notes and adhesive labels - some adhesives contain PFAS

What to Use Instead

• HDPE (high-density polyethylene) sample bottles - lab-supplied, certified PFAS-free
• HDPE or silicone tubing for pump systems
• Silicone O-rings instead of Viton
• Stainless steel or HDPE bailers (no PTFE check valves)
• Stainless steel or HDPE well caps - check that existing well caps don’t contain PTFE
• Nitrile gloves (powder-free) - change between each well
• Plain paper field notebooks with pencil or ballpoint pen
• Polypropylene containers are also acceptable for most methods

Pro tip: Order your sample containers from the analytical laboratory that will be running the analysis. They’ll supply containers that are certified PFAS-free for the specific method you’re using, with the correct preservative already added if required. Don’t try to source your own containers.

Clothing and Personal Care Restrictions

This is the part that surprises people the most. What you wear and put on your body before heading to the field matters.

Do NOT wear or use:

• Gore-Tex or any waterproof/breathable outerwear - treated with PFAS
• Scotchgard-treated or stain-resistant clothing - treated with PFAS
• Waterproof boots with PFAS-treated linings (most hiking boots)
• Sunscreen - many formulations contain PFAS
• Insect repellent with DEET - some formulations have PFAS in the carrier
• Cosmetics, foundation, or moisturizer - many contain PFAS
• Contact lenses - some solutions contain fluorinated compounds (debated, but some programs flag this)

What to wear instead:

• Untreated cotton or polyester clothing - nothing marketed as waterproof or stain-resistant
• Standard rubber rain gear if needed (PVC-based, not PFAS-treated)
• Plain Tyvek coveralls over your clothing
• Standard nitrile gloves - change frequently, especially between wells
• Untreated leather or rubber boots - check manufacturer specs if uncertain

If it’s going to rain, deal with it in non-PFAS rain gear or schedule for another day. A valid dataset is worth more than staying dry.

Lab Methods - Which One to Request

Choosing the right analytical method depends on what you’re sampling and why.

Drinking Water (Compliance and Screening)

Both methods require solid phase extraction (SPE) and are prescriptive - labs cannot modify the procedures. Method 537.1 requires samples be extracted within 14 days; Method 533 allows 28 days, which gives you more flexibility on shipping and lab turnaround.

For Ohio drinking water compliance work, either method is acceptable. If you’re not sure, ask your lab which one they recommend based on their turnaround time and your target analyte list.

Groundwater, Surface Water, Soil (Site Assessment)

Method 1633A is the current go-to for site assessment work. It covers the most PFAS compounds across the most media types, uses isotope dilution for better accuracy, and achieves detection limits low enough to screen against the 4 ppt MCLs. If you’re doing a Phase II or corrective action investigation and PFAS is a contaminant of concern, request 1633A.

Method 8327 is cheaper and faster (direct injection, no extraction step) but has higher detection limits. It’s fine for screening purposes where you’re trying to determine if PFAS is present at significant concentrations, but it may not be sensitive enough for drinking water pathway evaluations.

Field Procedure - Step by Step

Before You Leave the Office

1. Coordinate with the lab - confirm the method, get PFAS-free sample containers with preservative (if required), confirm holding times, and request sufficient containers for field blanks and equipment blanks
2. Check your clothing - lay out what you’ll wear the night before, confirm nothing is treated with PFAS
3. Inspect all equipment - verify no PTFE components. If using dedicated bladder pumps, confirm tubing is HDPE or silicone. If using a peristaltic pump, confirm tubing is silicone
4. Pack PFAS-free decon supplies - Alconox and DI water in PFAS-free containers. No Liquinox (it may contain fluorinated surfactants)
5. Review the site’s PFAS history - know what you’re looking for and what concentrations to expect

At the Well

1. Put on clean nitrile gloves before touching anything
2. Open the well and check for NAPL or sheen - note any visual observations
3. If collecting both PFAS and non-PFAS samples, collect PFAS first
4. Purge using low-flow procedures - same stabilization criteria as conventional sampling (pH, temp, SC, DO, ORP, turbidity). The only difference is equipment materials
5. Fill sample containers directly from the tubing discharge - slow, steady flow, minimize turbulence and splashing
6. Cap containers immediately after filling - don’t set them down open
7. Place samples in a cooler with ice - target ≤6°C. Use lab-supplied ice or bagged ice, not loose ice that could contact containers
8. Label containers using pre-printed labels or a PFAS-free marker - not a Sharpie on the container
9. Change gloves before moving to the next well

QA/QC Samples

PFAS QA/QC requirements are more extensive than conventional sampling because of the contamination risk:

• Field blank: One per sampling event. Fill a lab-supplied PFAS-free container with certified PFAS-free water in the field, using the same procedures as your samples. This catches contamination from field conditions.
• Equipment blank: One per equipment type per event (if using non-dedicated equipment). Run PFAS-free water through your decontaminated equipment and collect the rinsate.
• Trip blank: One per cooler. Lab-prepared PFAS-free water that travels with your samples but is never opened. Catches contamination during transport.
• Duplicate sample: At minimum one per 20 samples. Collected sequentially from the same source.

Do not skip blanks on PFAS sampling events. At 4 ppt MCLs, even minor contamination shows up, and without blanks you have no way to distinguish site contamination from sampling artifacts. Blank results above reporting limits can invalidate your entire dataset.

Common Mistakes

Mistake #1: Using existing well caps without checking them. Many monitoring well caps contain PTFE gaskets or O-rings. If you’re sampling existing wells for PFAS for the first time, check the caps before you start. Replace PTFE gaskets with silicone before sampling.

Mistake #2: Eating or drinking near sampling locations. Food wrappers, fast food containers, and many beverage containers contain PFAS. Keep food and drinks in the vehicle, away from the sampling area. Wash your hands after eating before handling samples.

Mistake #3: Using sunscreen. If it’s a sunny day, wear long sleeves and a hat instead. If you must use sunscreen, apply it hours before sampling and wash your hands thoroughly before gloving up. Better yet, avoid it entirely on PFAS sampling days.

Mistake #4: Forgetting about decon water. Your DI water for decontamination needs to be PFAS-free and stored in PFAS-free containers. Standard lab DI water stored in a carboy that’s also used for metals or VOC decon may be fine, but verify with your lab.

Mistake #5: Assuming your field equipment is clean. If you’ve used the same tubing or bailers for conventional sampling, residual PFAS from previous sites could be on your equipment. Either use dedicated PFAS-only equipment or decontaminate rigorously and run equipment blanks.

Mistake #6: Not communicating restrictions to the field team. If you have an inexperienced sampler or a driller helping on-site, they need to know the clothing and personal care restrictions too. Brief the entire field crew before the event. One person’s Gore-Tex jacket can contaminate everyone’s samples.

Homeowner and Private Well Testing

If you’re a homeowner concerned about PFAS in your drinking water, you don’t need to follow the full field procedures above - those are for professional environmental sampling. For home testing:

• Use a certified PFAS water test kit that includes prepaid shipping and lab analysis using EPA Method 533 or 537.1
• Follow the kit instructions exactly - the lab provides everything you need, including PFAS-free containers
• Run the tap for 2-3 minutes before collecting your sample (unless the kit says otherwise) to get water representative of your supply, not what’s been sitting in the pipes
• Ship the sample back the same day you collect it to stay within holding times

Results typically take 2-3 weeks. Compare your results to the federal MCLs: 4 ppt for PFOA and 4 ppt for PFOS.

Related Resources

• Ohio PFAS Standards - Drinking Water & Groundwater Action Levels - Current federal and Ohio-specific PFAS thresholds
• EPA PFAS Analytical Methods - Official method documentation
• ITRC PFAS Sampling and Analysis Guidance - Comprehensive technical reference