Per- and polyfluoroalkyl substances (commonly known as PFAS) are man-made chemicals that are key ingredients in (for example) non-stick cookware and firefighting foams because they have water-, oil- and heat-resistant properties.
Because PFAS are extremely chemically stable, these compounds are highly mobile, persistent, and bioaccumulative environmental contaminants. Exposure to these “forever chemicals,” as they are sometimes called, can lead to long-term health effects, including kidney and testicular cancer, high blood pressure, and even impaired development in infants.
Analytical scientists are working hard to detect a variety of samples that may contain PFAS, including food, but frequently encounter challenges in detecting and characterizing the compounds, including sample contamination and lack of instrument robustness.
Technology Network recently interviewed Dr. Holly Lee and Dr. Craig Butt from SCIEX to learn more about the analytical challenges of PFAS detection and how SCIEX’s 7500+ system is helping advance mass spectrometry methods to aid in PFAS detection.
Anna MacDonald (AM): What are the main challenges analytical scientists face when detecting and characterizing PFAS in food samples?
Holly Lee and Craig Butt (HL/CB): The two main challenges in PFAS analysis in food are sensitivity and matrix interferences. First, the detection limits of targeted methods are typically at low to high parts per trillion levels. These are trace-level concentrations, and detection requires high-performance mass spectrometers such as the SCIEX 7500+ system. Second, foods are inherently diverse and complex matrices, so thorough cleanup is required to minimize the effects of these matrices and ensure overall data quality. Finally, several known endogenous interferences in food matrices can cause false positives. For these interferences, high-resolution mass spectrometry is recommended to confirm PFAS detection.
AM: Tell us about the Mass Guard technology on the SCIEX 7500+ system and how it helps solve contamination issues and improves instrument robustness.
HL/CB: Mass Guard technology consists of hardware and software components that enhance and extend the robustness of the SCIEX 7500+ system while allowing users greater flexibility in managing system uptime. The hardware components consist of four T-shaped electrodes, called TBar electrodes, located in the Q0 region. These effectively act as bandpass filters to remove unwanted high m/z ions. In the same way that a guard column is used to protect the analytical column, the TBar electrodes selectively remove contaminating ions to produce a cleaner ion beam before entering the downstream mass analyzer elements. This anti-contamination protection has been demonstrated to help the SCIEX 7500+ system maintain optimal sensitivity for PFAS in food matrix extracts by more than 2x compared to the 7500 system.
The latest version of SCIEX OS software includes new features that make it easier for users to track, troubleshoot, and maintain their systems. For example, Metrics Tracker allows users to graph and monitor performance trends using system calibration, tuning data, and QA/QC assay data. It also provides built-in, automated contamination testing to troubleshoot poor sensitivity and inform upcoming maintenance actions.
AM: How does the SCIEX 7500+ system compare to the SCIEX 7500 system for PFAS analysis in food?
HL/CB: The quantitative performance of the 7500+ and 7500 systems is identical, meaning that both systems exhibit comparable ultra-trace level sensitivity and precision. However, the Mass Guard technology of the 7500+ system extended robustness by more than 2-fold during enhanced robustness testing compared to the 7500 system. Overall, sensitivity was maintained after over 7000 injections of food matrices on the 7500+ system. The Mass Guard technology of the 7500+ system extended the highest level of analytical performance over time.
AM: How was the robustness of each system tested? Why was this approach adopted?
HL/CB: Initial experimental testing with the 7500 system showed that sensitivity was maintained after a month of continuous food matrix analysis involving approximately 3000 injections. Therefore, to thoroughly test the robustness of the instrument, we adjusted the sample preparation to omit the final solid phase extraction polishing step. This resulted in food extracts that were slightly more aggressive but still representative of what our customers analyze. Food extracts were prepared from four separate matrices: salmon, avocado, spice powder and pet food, representing the diversity of food samples analyzed in a typical laboratory.
AM: What are the advantages of using uncorrected raw peak areas to measure instrument performance rather than IS-corrected peak areas?
HL/CB: Measuring raw, uncorrected peak areas is the true measure of instrument performance. IS corrected peak areas can mask loss of sensitivity as the instrument is affected by matrix contamination.
AM: Can you tell us more about the DJet+ assembly, how it improves serviceability for users, and how it impacts PFAS analysis workflows?
HL/CB: The DJet+ assembly is the key technology that captures and delivers ions to the Q1 region. This component is typically the first to become contaminated after the curtain plate and orifice and therefore requires regular cleaning to restore instrument sensitivity. On the 7500+, the DJet+ is user cleanable, allowing greater flexibility when maintenance is required.
AM: Are there any other features of the 7500+ system that you'd like to highlight?
The HL/CB:7500+ system also features fast multiple reaction monitoring acquisition speeds, enabling larger analyte panels to be processed in shorter run times without impacting sensitivity or data quality – a feature essential for large analyte panels such as pesticide and forensic drug screening.
Dr Holly Lee and Dr Craig Butt spoke to Anna MacDonald, Senior Science Editor at Technology Network.
About the interviewee
Dr. Holly Lee completed her PhD at the University of Toronto under Professor Scott Maberly, studying the biological and environmental processes involved in the fate of emerging PFAS precursors during post-consumer waste. After graduation, she worked for three years as a Senior Analytical Technologist at the Ontario Ministry of Environment, Conservation and Parks, where she developed and validated multiple methods for PFAS, pharmaceuticals, personal care products and other emerging contaminants. Since joining SCIEX in 2016, Holly has worked as an Applications Scientist, working on research and development of mass spectrometry software products such as SCIEX OS. Holly currently serves as the Global Technical Marketing Lead for all food LC-MS/MS applications.
Dr. Craig Butt received his PhD in Environmental Chemistry from the University of Toronto, where he studied the fate of PFAS in Arctic wildlife and the metabolism and atmospheric degradation of PFAS precursors. Craig then worked as a postdoctoral researcher at NSERC and a research scientist at Duke University, studying the in vitro toxicology and epidemiology of environmental contaminants. At SCIEX, he led method development for a variety of PFAS-specific applications, including EPA Methods 533 and 1633, human blood, and untargeted analysis of environmental samples.
