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PFAS Sampling System

PFAS Sampling System

The Apex Instruments PFAS Sampling System is based on the EPA Other Test Method 45 (OTM-45) for the isokinetic collection of PFAS from stationary sources. PFAS stands for per- and polyfluoroalkyl chemicals, which are found in a wide range of consumer products and facilities. PFAS can accumulate in the body and may lead to adverse health effects. Gaseous and particulate PFAS compounds are sampled isokinetically from an emission source and collected in a multi-component sampling train.

Our train is similar to the EPA Modified Method 5 Train used for semi-volatile compounds, with the addition of a second XAD-2 sorbent module for monitoring breakthrough. The stack gas is typically sampled for 4 hours at rate of less than 12.5 LPM to minimize the pressure drop across the XAD-2 module since high pressure drops across the resin can promote breakthrough. The filter, sorbent cartridge, and water impingers are recovered separately, and the glass components are rinsed with a methanol/ammonium hydroxide solution.

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Description

Apex Instruments PFAS Sampling System

Apex Instruments has developed a new PFAS glassware train based on the current EPA Method in development. The train is a modified method 5 system with the addition of our new compact vertical condenser and two additional XAD sorbent traps followed by knockout impingers.   

The OTM-45 train components consist of:

  • the front half glassware surfaces (nozzle, probe, and front half filter holder)
  • the glass fiber filter
  • the back half glassware surfaces (back half filter holder and condenser coil) and
  • the solid sorbent (XAD-2®) modules.
PFAS OTM-45 Isokinetic Train shown with GT Impingers

 

A vertical condenser is recommended by the method. In order to minimize glassware breakage during sampling, and to ease with sample recovery, a compact vertical condenser was developed to enable the glassware to fit into the standard Method 5 sample case.

The XAD-2 sorbent module has a 2:1 length to diameter ratio to increase the contact time between the sample gas and resin for adsorption efficiency. The module has a volume of 80 ccm and can hold up to 40 grams of XAD®-2 Polyaromatic adsorbent resin.

 

PFAS Sampling System Glassware with Compact Vertical Condenser and Two XAD Traps

Cross Contamination Avoidance

Sampling for PFAS without contaminating the samples can be challenging due to the prevalence of these chemicals in many consumer products and in standard sampling equipment. Apex Instruments seals our glassware with chemical resistant EPDM O-rings and DuraSeal™ film to avoid cross contamination. Lab and field personnel should pay special attention to avoid cross
contamination by carefully reviewing all materials that may come in contact with the samples.

OTM-45 Sampling Highlights

The stack gas is normally sampled for 4 hours at rate of less than 12.5 LPM to minimize the pressure drop across the XAD-2 module since high pressure drops across the resin can promote breakthrough. The filter temperature should be maintained above the gas dew point, but well below the standard temperatures used in Method 5 to prevent thermal decomposition of HFPO-DA (GenX) and other PFAS compounds. Sufficient ice should be added the impinger case to keep the condenser and sorbent module at a low temperature to minimize breakthrough of target analytes.

PFAS can be partitioned in stack emissions into several different fractions due to the physical properties of these species. At the elevated temperatures typically encountered in stack emissions the vapor pressure can be sufficiently high that some is present in the gas phase. The lower molecular weight fluorotelomer alcohols (FTOHs) have lower boiling points and so may primarily be present as vapors. PFAS can adsorb to particulate matter, are highly water soluble, and can dissolve in water droplets if present in the stack.

To measure these partitioned fractions, the stack effluent is sampled isokinetically (that is, the air enters the probe at the same velocity as it is moving in the stack, to accurately sample particles and droplets) and captured on a heated filter, an XAD-2 sorbent resin tube, and in water impingers. In some test programs a second XAD-2 sorbent cartridge is included in the sample train to determine if breakthrough has occurred. The filter, sorbent cartridge, and water impingers are recovered separately, and the sample train components are rinsed with a methanol/ammonium hydroxide solution.

PFAS Individual Glassware Components

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GN-3B
3-inch glass filter outlet, #28 unground O-ring ball
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3-inch glass filter inlet, #28 unground socket, 90-degree bend
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PFAS System Accessories

PTFE Filter Supports

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EPDM O-Rings

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Additional Information about PFAS

The widespread use of PFAS and their ability to remain intact in the environment means that over time PFAS levels from past and current uses can result in increasing levels of environmental contamination. 

Materials with the potential to introduce bias include, but are not limited to:

  • Teflon, Polytetrafluoroethylene (PTFE)
  • Waterproof Coatings Containing PFAS
  • Fluorinated Ethylene-propylene (FEP)
  • Ethylene Tetrafluoroethylene (ETFE)
  • Low-density Polyethylene (LDPE)*
  • Polyvinylidene Fluoride (PVDF)
  • Pipe Thread Compounds and Tape

*LDPE doesn’t contain PFAS in the raw material but may contain PFAS cross-contamination from the manufacturing process. Test prior to use to be safe.

PFAS can be found in:

  • Food packaged in PFAS-containing materials, processed with equipment that used PFAS, or grown in PFAS-contaminated soil or water.
  • Commercial household products, including stain- and water-repellent fabrics, nonstick products (e.g., Teflon), polishes, waxes, paints, cleaning products, and fire-fighting foams (a major source of groundwater contamination at airports and military bases where firefighting training occurs).
  • Workplace, including production facilities or industries (e.g., chrome plating, electronics manufacturing or oil recovery) that use PFAS.
  • Drinking water, typically localized and associated with a specific facility (e.g., manufacturer, landfill, wastewater treatment plant, firefighter training facility).
  • Living organisms, including fish, animals and humans, where PFAS have the ability to build up and persist over time.