PFAS in Sediments
Per- and polyfluoroalkyl substances (PFAS) have been produced for 70 years and are currently the subject of increasingly intense environmental research due to their mobility and toxic effects in the environment. Despite often being referred to as a single class of chemicals, the chemistries of individual PFAS analytes vary greatly, from highly mobile short-chain acids to long-chain sulphonates. Physical and chemical properties dictate PFAS mobility and govern the extent of interaction with surrounding matrices or environmental contamination. In particular, the matrix properties of solid environmental samples, such as sediments, can significantly affect PFAS mobility and analytical recovery. Understanding the properties of a sediment sample is central to producing quality data.
Difficulties of Sediment Analysis
Sediments contain a mixture of organic matter and minerals from weathered rock, soils, and aquatic life, as well as chemicals from local human activity, including PFAS. Depending on local conditions, these chemicals can accumulate in the sediments and then later be released to the surrounding environment. As a result, sediments are key to understanding the local environment but can pose difficulties for PFAS analysis due to the complexity of the matrix. There are a number of items to consider when developing robust sediment methods:
- Sediments are a diverse class of samples – No two sediment samples are the same. Sediments are constantly in flux and require robust analytical methods to account for sample variations.
- PFAS can stratify within a sediment sample – The wide range of PFAS chemistries means that parts of the target analytical list can migrate into different components of the sediment. Migration patterns can also change once the sediment is removed from its dynamic environment.
- Organic matter and mineral content – The different types of organic matter and minerals found in sediments can bind PFAS within the sample matrix, resulting in poor recoveries. Other types of material can suppress recovery by disrupting extraction and sample cleanup chemistries.
- Interfering contamination – In environments with PFAS contamination, other human-made chemicals may be present. Such chemicals can also bind PFAS within the matrix, disrupt the extraction chemistry, or co-extract with the target analytes and cause interference patterns during analysis.
Our Expertise in Sediment Analysis
To mitigate challenges during sediment analysis, Enthalpy Analytical deploys and refines best practices and technologies to ensure high-quality data are delivered to our clients.
- Representative samples – All sediment is thoroughly homogenized and inspected to ensure that the components are fully mixed and that any clumped material is broken down. This process is repeated just before each sub-sample is prepared for analysis.
- Accurate and robust methodologies – To accurately quantify PFAS in sediment, Enthalpy utilizes isotope dilution, a method of quantitation that adds isotopically labeled PFAS to a sample before the extraction takes place. The isotopically labeled PFAS are chemically identical to the target PFAS and are allowed to distribute within the sample in the same way as the target PFAS. Any inefficiency of recovery of the labeled standards allows us to correct the concentrations of the target PFAS. This process is vital for complex matrices, such as sediment.
- Sample cleanup – Our methods use a range of extraction and cleanup chemistries to exclude and remove interfering matrix components. We continue to improve our methods as new technologies become available and as PFAS target lists expand.
- Instrument sensitivity – Enthalpy has 13 industry-leading ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) instruments dedicated to PFAS analysis. We select the most sensitive instruments on the market and develop the data acquisition procedures to isolate target PFAS chromatography from known interfering chemicals.
- Data review by knowledgeable PFAS scientists – Even while employing the above steps and the latest technology, some matrix effects are still observed. Enthalpy employs a team of liquid chromatography and PFAS data experts to assess each sample. Their in-depth knowledge is key to both improving our methods for sediment analysis and helping our project management team ensure clients understand their complete data reports.
Choose PFAS Testing Experts
When choosing a laboratory for your PFAS testing needs, it is important to select one that understands the difficulties of measuring ultra-trace contaminants in environmental samples. At Enthalpy, we take pride in our robust analytical methods and technical understanding of PFAS data. Regardless of whether you are testing sediments or other materials, having a trusted partner that can guide you through selecting the best analytical solution gives you confidence that your data will be useful and that your project will be a success.
To learn more about our PFAS testing services, please reach out using the form below.
Oliver Cawdell
Oliver is the Laboratory Technical Director for Enthalpy Analytical in El Dorado Hills, California, and has been with the company for 5 years. He has worked in the environmental industry for 15 years, starting out as an environmental consultant before focusing on analytical data quality and method development. Through his years at Enthalpy, Oliver has championed the research and development of PFAS analyses, building robust isotope dilution assays for a range of environmental and non-standard matrices.
