Navigating USEPA 1633 Regulations for PFAS Analysis with LC-MS/MS

Waters Corporation | Kari Organtini, Ken Rosnack

Introduction?

Per- and polyfluoroalkyl substances (PFAS) have become a subject of widespread concern due to their persistence and potential health hazards. The United States Environmental Protection Agency (USEPA) takes center stage in regulating these compounds. In this blog post, we will explore the versatile USEPA Method 1633 and its significance in PFAS analysis using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) across a diverse range of environmental matrices.?

USEPA Method 1633: A Comprehensive Approach?

PFAS, an extensive group of synthetic chemicals, have been employed in various applications, ranging from non-stick cookware to firefighting foam, presenting challenges in monitoring and regulation due to their ubiquity in the environment.?

Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) stands at the forefront of PFAS analysis due to its unmatched sensitivity and selectivity. This method facilitates the separation and quantification of PFAS compounds based on their chemical properties and mass spectrometry data.?

USEPA Method 1633 has emerged as a versatile protocol designed to address the complexity of PFAS compounds. It encompasses the analysis of 40 PFAS compounds, including various isomers and compounds falling under nine distinct classes. The broad array of compounds analyzed extends its relevance to a wide spectrum of environmental matrices.?

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Key Steps in USEPA 1633 Analysis:?

1. Sample Collection: The process of sample collection in accordance with USEPA Method 1633 is a meticulous endeavor. It starts with selecting appropriate sampling containers that are free of PFAS contaminants. Proper decontamination procedures for sampling equipment are vital to avoid cross-contamination. Samples are collected in a manner that prevents?contamination. The correct documentation of sample collection conditions, including date, time, location, and sample handling practices, is crucial for data integrity.?
2. Sample Preparation: Sample preparation in USEPA Method 1633 is an essential step that ensures that the collected samples are suitable for analysis. The method details the process of sample extraction and purification. Samples are typically subjected to solid-phase extraction (SPE) using specific cartridges designed for PFAS compounds. These cartridges selectively retain PFAS compounds while other interferences are washed away. During sample preparation, the use of Graphitized Carbon Black (GCB) is used to further clean up the sample. The addition of GCB into routine sample preparation is an important addition that distinguishes USEPA Method 1633 from previous PFAS methods. The SPE process is meticulously documented to ensure traceability and data quality.?
3. Chromatographic Separation: The chromatographic separation in USEPA Method 1633 is a crucial aspect of the analysis. The method employs a liquid chromatograph with a specialized column that can separate PFAS compounds based on their chemical properties. The separation is optimized to distinguish between various PFAS compounds, including structural isomers and compounds belonging to different classes, as well as potential sample interferences. Chromatographic conditions, including mobile phase composition, flow rates, and column temperature, are carefully controlled to achieve the desired separation.?
4. Mass Spectrometry: Mass spectrometry is a core component of USEPA 1633 analysis. Once the PFAS compounds are separated by the chromatograph, they are introduced into the mass spectrometer. Here, the compounds are ionized using an electrospray ionization source. ?In the case of LC-MS/MS analysis of PFAS, the mass spectrometer captures multiple reaction monitoring (MRM) chromatograms, enabling exceptional sensitivity and selectivity by precisely measuring the mass-to-charge ratio (m/z) of ions. This approach facilitates the identification of specific PFAS compounds through their distinctive mass spectra. The method specifies the use of triple quadrupole mass spectrometers, known for their exceptional sensitivity and selectivity in detecting PFAS compounds.?
5. Data Analysis: Data analysis in USEPA Method 1633 involves the use of specialized software that processes and conveniently displays the mass spectrometry data. ?The software helps the user with compound identification and quantification by matching the MRM and retention time of the analyte with a reference standard. Calibration curves generated using certified standards are used to quantify the concentration of individual PFAS compounds in the sample. Data quality control procedures, including instrument calibration and method blanks, are implemented to ensure the reliability and accuracy of the results. Detailed record-keeping and documentation of the entire analytical process are essential for traceability and data integrity.?

These detailed steps in USEPA Method 1633 analysis ensure that the analysis is rigorous, consistent, and capable of providing accurate and reliable data on PFAS compounds in various environmental matrices.?

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Adapting to Challenges, Leveraging Advantages?

Analyzing PFAS through LC-MS/MS encounters challenges, given the multitude of PFAS compounds and their presence at low concentrations. Nevertheless, LC-MS/MS presents many advantages, such as its high sensitivity, accuracy, and capacity to distinguish between individual PFAS compounds. This technique can be applied to various sample matrices, spanning from drinking water and wastewater to soil, biosolids, tissues and other environmental samples.?

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Conclusion?

USEPA Method 1633, in conjunction with LC-MS/MS, offers an invaluable tool for the regulation and analysis of PFAS compounds across a wide spectrum of environmental matrices. As concerns regarding PFAS' environmental and health implications continue to grow, this method provides a standardized and comprehensive approach to assess the presence and concentrations of these compounds. As technology and analytical methods advance, we can anticipate even more refined and efficient techniques for PFAS analysis in the future.?

Are you looking to conquer your PFAS analysis from sample prep to proficiency testing? Team up with Waters and strategize your analytical game plan today with our PFAS Resource Hub.

#PFAS #USEPA #LCMSMS #WaterTesting #MassSpectrometry