Perfluoro-1-octanesulfonic acid (PFOS), Perfluoro-n-octanoic acid (PFOA), and Other Perfluoroalkyl Substances (PFASs)

RTI Testing Capabilities

RTI has developed internal methods in conjunction with the testing procedures referenced below for measuring PFASs or polyfluorinated compounds (PFCs), such as perfluoro-1-octanesulfonic acid (PFOS) and perfluoro-n-octanoic acid (PFOA), in water and soil.  The laboratory has LC/MS/MS systems that have undergone method validation and are capable of meeting reference method guidelines.  RTI has processed aqueous and solid samples through the extraction and analytical procedures, performed demonstration of method performance, determined detection limits, quantification limits, assessed the accuracy and precision of the procedures, performed recovery assessment of spiked matrices and has developed standard operating procedures for the analysis of PFASs.

What are perfluoroalkyl substances (PFASs), such as PFOS and PFOA?

PFASs are a class of synthetic chemicals with numerous industrial and commercial applications with an extensive number of compounds that can be included in this classification. These compounds are primarily carboxylic acid or sulfonic acids (sulfonates) with completely fluorinated alkyl groups of various lengths (can occur as linear or branched chains).  PFCs and perfluorinated alkyl acids (PFAAs) are additional terms referring to this class of chemicals.   PFASs have been used in a wide range of consumer products, have industrial applications in the electronics and aerospace industries and in aqueous film-forming foams (AFFFs) used for firefighting training.  The two most commonly encountered compounds in the environment are PFOS and PFOA.  Due to increasing concern for potential health effects associated with these compounds, PFOS is no longer produced in the United States and PFOA is currently being phased out of production.

Environmental and Health Impacts of PFOS/PFOA?

PFAS compounds, especially the longer chain chemicals, do not easily degrade and can persist in the environment for a significant amount of time.   Due to widespread use, PFAS such as PFOS and PFOA are prevalent throughout the environment, resulting in contamination of drinking water, surface water, and soil.  The highest concentrations are typically encountered in areas in close proximity to facilities where firefighting training has occurred, industrial production facilities, and discharge from waste water treatment plants (both in effluents and bio solids).  As a result of their widespread presence in the environment, human exposure to PFAS compounds occurs through use of commercial products, drinking water, air, and dust.  Studies have indicated that these compounds are present in virtually all individuals.  PFAS have been linked to potential health effects including cancer, disruption of endocrine activity, reduced immune system function and impairment of various organs.  The EPA and several States have developed human health guidelines for exposure to PFOS and PFOA.  Several years ago, manufacturers began to replace the previously produced long chain PFASs with short chain PFASs.  Data on human health effects for the shorter chain PFASs is limited, but adverse effects from exposure have been indicated in some studies.

Testing Procedures for PFASs in Drinking Water

In response to concerns over PFASs in drinking water, the EPA published Method 537 in 2008 and an updated Version 1.1 in 2009.
This method establishes analytical procedures for determining PFAA concentrations in drinking water.  Method 537 list fourteen PFAA compounds and specifies the analytical protocol for the extraction and instrumental analysis. 

Method 537 Summary: An aliquot of a water sample is fortified with surrogates and passed through a polystyrenedivinylbenzene solid phase cartridge, which captures the analytes of interest.  The cartridge is eluted with a minimal volume of methanol and concentrated to dryness with nitrogen in a heated water bath.  A methanol:water solution is added to the extract and adjusted to the desired final volume (typically 1 mL) after addition of internal standards.  An aliquot of the extract solution is introduced into a Liquid Chromatograph (LC)/Tandem Mass Spectrometer (MS/MS) system equipped with a C₁₈ column and data system.   Comparison of the retention time and resulting mass spectra to reference standards used for instrument calibrations allows for identification of the compounds of interest.  The concentration of analytes identified is determined by internal standard calibration techniques. 

Two other recent methods have been published by ASTM for the analysis of PFCs in soil (ASTM Method D7968) and PFCs in water, sludge and influent samples (ASTM Method D7979).  Both of these procedures specify the use of LC/MS/MS as the analytical technique.

Method Performance

Due to enhanced sensitivity, the use of LC/MS/MS allows quantification of PFAS compounds in the parts per trillion (ppt) range.  Coupled with the determinative capability of tandem mass spectrometry, this method allows for the definitive assay of PFASs at trace levels in drinking water and other applicable matrices.  Method 537 specifies establishing Minimum Reporting Levels (MRL) for each compound.  This procedure determines the lowest concentration of analyte that can be measured with a high degree of confidence.  Tuning and calibration procedures ensure optimization of the instrument for the analysis of PFASs.  Specifications for establishing and verifying the calibration curve are required to be met prior to sample analysis.  System monitoring is assessed throughout the analytical event through various quality control evaluations.  System cleanliness is monitored through routine analysis of laboratory reagent blanks and supplied field blanks.  Performance is assessed through monitoring the recovery of surrogates, laboratory fortified blanks, laboratory fortified matrix samples and internal standards.

Applications for Testing

The concern for potential health effects associated with PFAS compounds, such as PFOS and PFOA, and their persistence in the environment requires that sampling and testing monitoring programs be established to assess the extent and degree of PFAS contamination in the environment.  Drinking water monitoring will be necessary to evaluate current levels and allow determination of compliance with current advisory guidelines and future established standards.  Department of Defense programs have been implemented to assess the extent of PFAS, especially PFOS and PFOA, contamination at military facilities that have extensively used these chemicals in firefighting training exercises.  Monitoring of surface water will be required to determine potential effects on aquatic life and human exposure.  Areas that may be impacted by various manufacturing and application processes will also require environmental assessments of soil and groundwater to evaluate possible impacts.