Formatted Title
Applications of the Sentinel™ Passive Sampler for PFAS Measurement in Environmental Waters
Background/Objectives
The Sentinel™ passive sampler was designed to measure per- and polyfluoroalkyl substances (PFAS) in a variety of water types, including groundwater, surface water, stormwater, and sediment porewater. Passive sampling devices for environmental water testing reduce the time required for sampling and analysis, volumes required for analysis, and amount of investigation derived waste, thereby decreasing monitoring costs and providing health and safety advantages. Furthermore, the Sentinel passive sampler is an integrative (accumulating) sampler, which provides a distinct ability to determine time-averaged concentrations of analytes of interest over the deployment period. The Sentinel passive sampler is a small device comprised of a high-density polyethylene housing containing a modified organosilica resin held in place by open mesh polypropylene screens, which allows direct contact with the sampled water. Accumulated PFAS mass is extracted in the analytical laboratory and converted to aqueous concentration. The 2021-2022 results from four field testing sites have previously been published. Several hundred passive samplers at more than seven unique sites will have been field-deployed by the 2024 conference date, and new data will be presented. The Sentinel passive sampler is commercially available for purchase and analysis is offered by several commercial laboratories in the United States and Europe.
Approach/Activities
Following initial pilot testing, Sentinel passive samplers have been deployed in multiple additional sites in a variety of environmental waters, representing a wide range of PFAS concentrations and geographic settings. Conventional grab samples were collected for comparison at several sites. Passive sampler extraction and analysis methods have been extended to allow analysis of all 40 of the EPA Method 1633 analytes. Passive samplers were previously calibrated for surface water and groundwater applications.
Results/Lessons Learned
The Sentinel passive sampler is a fully developed, commercially available technology for PFAS sampling and laboratory analysis using established methods (modified U.S. EPA Method 537.1, 1633, German DIN 38407-42). The sampling rates, that is, PFAS uptake rates onto the passive sampler, have been calibrated across a broad range of water flow rates (sediment porewater, groundwater, and surface water) and temperature to allow precise determination of PFAS concentration in the water sample from the mass accumulated on the sampler. Passive sampler results are largely unaffected by ionic strength, pH, temperature, ORP, and humic acid content. Achievable limits-of-detection (LODs) are typically 1 part per trillion; field results are reproducible, with 15-30% relative standard deviation in replicate samplers. Previous comparison between grab sample and passive sample results indicates strong correspondence (typically within 2X difference) over 5 orders of magnitude in concentration (0.5-150,000 ng/L). Field deployment times are flexible, with recommended times of 3 to 45 days based on laboratory results. Example project applications and recommendations for monitoring program design, implementation, and stakeholder acceptance will be discussed.