With the growing awareness of PFAS, analytical needs are ever-changing. The number of individual PFAS compounds of interest continues to increase, and the requested levels of detection continue to decrease. While thousands of compounds meet the definition of a PFAS, individual regulations and analytical methods focus on anywhere from 20 to 70 specific chemicals. For each PFAS compound analyzed, an analogous surrogate compound is needed for instrument calibration and compound quantification. The limited availability of PFAS surrogate compounds presents another analytical challenge to the expansion of the target PFAS analysis list.
Method reporting and detection limits (MRL and MDL) for the priority pollutant organic compounds, such as benzene or naphthalene, are typically in the parts per billion (ug/l) range, while MRLs for PFAS are 1000 times lower in the parts per trillion (ng/l) range. While the UCMR5 (Fifth Unregulated Contaminant Monitoring Rule) Laboratory Approval Program found that most participating laboratories reported MRLs less than 4 ppt, not all commercial laboratories will be able meet these limits.
PFAS are ubiquitous in our daily lives, making it difficult to acquire water samples free of potential interfering contamination. PFAS are present in certain water-resistant clothing, fabric softeners, cosmetics, hand cream, sunscreen, notepads, markers, Teflon, food packaging, and more. Because traditional compounds of interest do not sorb to Teflon, the material is commonly used in sampling and analytical equipment. Field samplers need to be aware of all possible PFAS sources and ensure that none are present during sample collection. Combined with what the field samplers could potentially introduce, the environment in which the sample is collected must also be PFAS-free. The potential for introducing contamination into a sample at the time of collection is a constant challenge considering the trace levels of these proposed MCLs.
Generating high-quality, accurate PFAS data starts with selecting a competent sampling team and an analytical laboratory. And then, at the end of the day, once PFAS data are generated, extensive quality control assessments by analytical chemists knowledgeable in the nuances of the PFAS sample collection and analysis are required to assess the data’s accuracy, precision, and representation to ensure that the data are suitable to support project decisions.
Given the increasing requirements for PFAS analysis and the technical challenges associated with obtaining high-quality data, commercial laboratories may have difficulties keeping up with the demand. Given the challenges of collecting and analyzing environmental samples for PFAS compounds, care and oversight are required to obtain high-quality and accurate data generation. Where possible, staff experienced in PFAS sample collection should be available to oversee sample collection efforts, and laboratories should be audited prior to the initiation of projects. Laboratory-generated data obtained through one’s effort or from other parties should be inspected and validated by trained staff to assess the accuracy and precision of the results.