Chromatography
New Concerns about PFAS in Food: The Convergence of Environmental Contamination and Food Safety
David C. Kennedy, PhD, Phenomenex, Inc, Torrance, CA, USA Email:
DavidK@phenomenex.com
Per and Polyfl uorinated Alkyl Substances (PFAS) are well known environmental contaminants that have a newly recognised potential to taint certain food products through agricultural consumption via environmental transport from contaminated industrial sites [1]. The analysis of PFAS in food products requires more extensive analytical preparation techniques, compared to PFAS testing of simple matrices such as drinking water, in order to reduce the impact of sample matrix interferences on the subsequent instrumental analysis. An example is provided of a PFAS method applicable to milk, butter, cheese and fi sh.
The Prequel
Per and Polyfl uorinated Alkyl Substances (PFAS) are an extensive family of synthetic, fl uorochemicals with a unique set of physical and chemical properties. These properties have resulted in their widespread commercial use over the past 50 years in diverse applications ranging from fi re fi ghting foams to stain resistant carpet to grease-proof pizza boxes. However, these same unique physical and chemical properties also have been found to bear serious environmental consequences: widespread dispersion ability, extreme environmental persistence and a high degree of bioaccumulation [2]. Although PFAS do not exhibit acute toxic properties, researchers have found that PFAS can demonstrate a large number of subtle, chronic health effects, primarily affecting the endochrine and reproductive systems. Consequently, health experts have long been concerned that low- level, cumulative exposure to PFAS over an extended period of time could have serious health consequences [3]. Therefore, chronic lifetime PFAS exposure pathways - such as through food or drinking water – are of particular concern to regulators and are receiving enhanced scrutiny.
Initial Concerns
In the US, the initial US Food and Drug Administration (FDA) concern about PFAS centered about the contamination of food products through contact with PFAS containing food packaging (and to a lesser extent with food processing equipment). The classic examples are those PFAS coated pizza boxes, fast-food hamburger wrappers and microwave popcorn bags that have done such a marvelous job of keeping grease off our clothes. That problem was summarily solved in late 2016 when FDA removed the approval for the use of PFAS in food packaging [4].
Likewise, the primary US Environmental Protection Agency (EPA) focus has been on drinking water as a primary source of lifetime PFAS exposure. EPA is continuing to conduct extensive nationwide testing for PFAS in drinking water under the Unregulated Contaminant Monitoring Rule (UCMR) program [5]. These efforts will very likely result in specifi c regulatory limits for the allowable concentration of certain PFAS in drinking water.
Concurrently, other government agencies, such as the US Department of Defense (DOD) have been extensively studying the widespread environmental contamination of military facilities owing to the extensive historical use of PFAS fi refi ghting foams, principally at air bases [6].
Convergence
Initially, these three individual trains of concern seemed to be running on separate tracks. It was only more recently that they were seen to be converging toward a much larger, more complex problem requiring multimedia, multi agency examination and the use of more sophisticated analytical tools. The simplifi ed pathway model shown in Figure 1 illustrates the general scope of the problem. By the end of 2019, the FDA was fully on board with concerns about PFAS entering the general food supply through environmental sources, potentially leading to the contamination of dairy products, bottled water, seafood and other consumables [7].
Analytical Implications
This expanded concept of the PFAS problem is clearly a major step forward, but it has presented some analytical challenges. Much of the offi cial PFAS methodology developed over the past decade has been focused on the analysis of drinking water and aimed at a very limited list of analytes. With little challenge from matrix interference, easily surmountable chromatography issues and straight forward mass spectrometry, these offi cial drinking-water-only methods proved to be inadequate when applied to the analysis of PFAS in soil, sediment, sludge and wastewater. When applied to the analysis of foods - with a myriad of complex matrices, they are quite ineffective, resulting in a surge in PFAS analytical method development centered about complex matrices, with food testing occupying a prominent position. The following section features one such application as an illustration of the approaches now being pursued in pursuit of the expanded PFAS challenge.
Analysis of PFAS in Dairy Products, Eggs, and Fish by LC-MS/MS
Method Introduction. The following work was performed through a collaboration between Weck Laboratories, Inc, City of Industry, CA, USA and Phenomenex, Inc, Torrance, CA, USA, for the development of new sample preparation and analysis procedures for determining low levels of PFAS in food products. This particular application was directed at achieving sub-ppb sensitivity for 23 PFAS analytes in dairy products (milk, butter and cheese), eggs and fi sh as representative of diffi cult to analyse fatty matrices. The following discussion is a synopsis of the full work [8].
Figure 1. Pathway Model for Environmental Transmission of PFAS to Food and Consumer
Sample Preparation. One gram of homogenised sample was spiked with internal standards and surrogates and an analyte mix of 23 PFAS compounds (Table 1) at the 1ng/g level, followed by the addition of 10 mL acetonitrile and 10 ml water. Four replicates of each matrix (milk, eggs, butter, cheese and fi sh) were prepared. The samples were processed by a modifi ed
Table 1. PFAS Analyte List .
INTERNATIONAL LABMATE - FEBRUARY 2021
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