New Developments in Analytical Systems May Aid the “Fight” Against PFAS

Perfluoroalkyl and polyfluoroalkyl substances (commonly known as PFAS) are manmade chemicals that are key components for (e.g.) non-stick cookware and firefighting foams due to their water and oil repellency and temperature resistance.

The extreme chemical stability of PFAS makes these compounds highly mobile, persistent and bioaccumulative environmental contaminants. Exposure to these “forever chemicals” (as they’re sometimes known) can lead to long-term health consequences, including kidney and testicular cancer and high blood pressure, in addition to complications in infant development.

Analytical scientists have “all hands to the pump” detecting the vast array of samples PFAS may be present in, including food. However, challenges, such as sample contamination and a lack of instrument robustness, are frequently encountered when detecting and characterizing the compounds.

Technology Networks recently spoke with Dr. Holly Lee and Dr. Craig Butt from SCIEX to learn more about the analytical challenges of detecting PFAS and SCIEX’s 7500+ system, which can help advance developments in mass spectrometry, aiding PFAS detection.

Anna MacDonald (AM): What are some of 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 of PFAS analysis in food are sensitivity and matrix interferences. First, target method detection limits are typically in the low-to-high part-per-trillion levels. These are trace-level concentrations and require a high-end mass spectrometer such as the SCIEX 7500+ system for detection. Second, food is an inherently diverse and complex matrix requiring extensive clean-up to minimize these matrix effects and ensure overall data quality. Finally, several known endogenous interferences in food matrixes can result in false positives. For these interferences, high-resolution mass spectrometry is recommended to confirm PFAS detections.

AM: Can you tell us about the Mass Guard technology in the SCIEX 7500+ system and how it helps to address contamination issues and improve instrument robustness?

HL/CB: The Mass Guard technology consists of hardware and software components that enhance and extend the SCIEX 7500+ system's robustness while increasing user flexibility in managing system uptime. The hardware component consists of four T-shaped electrodes, called TBar electrodes, in the Q0 region. These effectively act as a bandpass filter 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 it enters the downstream mass analyzer elements. This contamination-busting protection was demonstrated to more than double improvements in maintaining optimal sensitivity of PFAS in food matrix extracts on the SCIEX 7500+ system compared to the 7500 system.

The latest version of SCIEX OS software offers new features to facilitate user-directed system tracking, troubleshooting and maintenance. For example, the Metrics Tracker enables the user to chart and monitor performance trends using system calibration, tuning data and QA/QC assay data. Automated built-in contamination tests are also available for users to troubleshoot during sensitivity loss and help inform them of further 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+ system and 7500 systems are identical. That is, both systems show comparable ultra-trace level sensitivity and precision. However, the 7500+ system Mass Guard technology extended the robustness by greater than two-fold during our enhanced robustness tests compared to the 7500 system. Overall, the sensitivity was maintained after >7000 food matrix injections on the 7500+ system. The Mass Guard technology of the 7500+ system extended the highest level of analytical performance over a longer period of time.

AM: How was the robustness of each system tested? Why was this approach taken?

HL/CB: Our initial experimental tests with the 7500 system showed that the sensitivity was maintained after one month of continuous food matrix analysis, comprising ~3000 injections. Therefore, we adjusted the sample preparation to omit the final solid-phase extraction polishing step to thoroughly test the instrument's robustness. This resulted in a slightly more aggressive food extract but was still representative of what customers analyzed. The food extracts were prepared from four separate matrixes – salmon, avocado, spice powder and pet food – representing the diversity of food samples a typical lab analyzes.

AM: What are the advantages of measuring instrument performance using uncorrected raw peak areas rather than IS-corrected peak areas?

HL/CB: Measuring the uncorrected raw peak areas is the true measure of instrumental performance. IS-corrected peak areas can hide the sensitivity loss as an instrument is impacted due to matrix contamination.

AM: Can you tell us more about the DJet+ assembly, how it improves user serviceability and the impact this has on PFAS analysis workflows?

HL/CB: The DJet+ assembly is a critical piece of technology that captures and transmits ions into the Q1 region. This component is typically the first to become contaminated – after the curtain plate and orifice – and requires periodic cleaning to restore instrument sensitivity. In the 7500+, the DJet+ can be cleaned by the user, ultimately increasing flexibility when maintenance is required.

AM: Are there any other features of the 7500+ system that you would like to highlight?

HL/CB: The 7500+ system is also capable of fast multiple reaction monitoring acquisition speeds, allowing larger analyte panels during shorter run times without impacting sensitivity and data quality. This feature is vital for large analyte panels such as pesticides and forensic drug screening.

Dr. Holly Lee and Dr. Craig Butt were speaking to Anna MacDonald, Senior Science Editor for Technology Networks.

About the interviewees

Dr. Holly Lee completed her PhD with Professor Scott Mabury at the University of Toronto, studying the biological and environmental processes involved in the fate of novel PFAS precursors upon consumer disposal. Following graduation, she worked as a Senior Analytical Technologist at the Ontario Ministry of the Environment, Conservation and Parks for three years during which she developed and validated multiple methods on PFAS, pharmaceuticals and personal care products and other emerging contaminants. Since joining SCIEX in 2016, Holly has worked as an application scientist involved in the research and development of mass spectrometry software products like SCIEX OS. Currently, Holly is the global technical marketing lead for all food LC-MS/MS applications.

Dr. Craig Butt obtained his PhD in environmental chemistry at the University of Toronto, where he investigated the fate of PFAS in arctic wildlife and the metabolism and atmospheric degradation of PFAS precursors. Craig was then an NSERC postdoctoral research fellow and research scientist at Duke University, researching in vitro toxicology and epidemiology of environmental contaminants. Within SCIEX, Craig has led method development for various PFAS-specific applications, including EPA Methods 533 and 1633, human blood and nontargeted analysis of environmental samples.