The monitoring of per- and polyfluoroalkyl substances (PFAS) into food is an important environmental and health concern. Raquel Sendón García, PhD, is a Faculty Member in the Department of Analytical Chemistry of Nutrition and Food Science, and a Faculty of Pharmacy member at the University of Santiago de Compostela in Spain. She has been performing research on food contamination and the presence of potentially harmful chemicals in foods for some time. We recently spoke to her about her work using GC–MS, HPLC, LC–MSn, and other analytical techniques to analyze PFAS migration into food from packaging materials.
You have published a book on the subject of food contamination from packaging materials (1). What key aspects have you learned from your research about migration of chemicals from food contact materials into food?
Probably the key is the knowledge about what are the substances that can migrate from food contact material. Each food contact material is different, and its composition and how it is made are critical points that affect the possible migration of substances, once the food contact material is used. So, for researchers and for the risk evaluation of these materials, the more information they have on its composition, the more effective the risk evaluation will be. But this is a hard task especially for those materials that are obtained after a long production chain that involves several processing industries.
What concerns you most about PFAS in food samples? What can be done to reduce exposure for humans and pets?
I think that the main concern is that these PFAS substances are very stable, they do not break down or undergo other chemical reactions in the environment, so even though the production of some of them are banned in the USA and in Europe, it will be very difficult to avoid their presence in foods. For this reason, to reduce exposure, in my opinion, it is necessary to monitor the levels of PFAS in food contact materials and in food. To monitor PFAS substances is a challenge due to the chemical complexity of foods and also to the complexity of PFAS compounds.
You have studied a variety of plastic packaging materials using purge and trap (P&T) coupled to GC–MS for volatile compounds and GC–MS for semivolatile compounds after extraction with organic solvents (2). What discoveries were most surprising to you related to migration of chemicals from plastic packaging into food simulants?
The most surprising discovery is related with the use of P&T for the analysis of compounds present in plastic packaging materials, that could migrate. As you say we used P&T coupled to GC–MS to determine volatile compounds, but the most surprising was that this technique has allowed us to detect compounds with relatively high boiling points, as for example butylated hydroxytoluene (bp: 265 ºC) caprolactam (bp: 270 ºC) or diethyl phthalate (bp: 295 ºC).
You have published research to characterize the migration into food of internal can coatings made from synthetic polymers known as epoxy-based resins, mainly based on bisphenol A diglycidyl ether (BADGE) using HPLC-FLD and LC–MS/MS (3). What did you conclude from these studies?
Although this topic might seem outdated (my PhD work was related to the analytical determination of BADGE and some related compounds nearly 20 years ago), these types of coatings are still used as internal coatings of food cans, and some of the compounds that migrate are still not being considered potentially harmful in exposure assessments.
You have also studied the migration of several polyester-based coatings intended for food contact using Fourier transform infrared spectroscopy with attenuated total reflectance (ATR-FT-IR), and confocal Raman microscopy to identify this type of coating (4). How successful were these techniques for chemical identification?
Both techniques are powerful in terms of identification of materials, which it helps to focus the task of identifying the potential migrating substances, moreover if you have a complete library of spectra, you can identify very accurately the coating material. The main drawback of ATR-FT-IR is that if the coating is composed of two or more layers, the depth of light penetration does not allow the differentiation of these layers—the infrared energy does not penetrate more than 1–2 µm, depending upon the wavelength and other optical and chemical parameters). But in these cases, confocal Raman microscopy completes this gap, because it is very helpful since this technique allows one to differentiate the different material layers, as was demonstrated in the previously mentioned work.
You also have investigated using gas chromatography coupled to mass spectrometry (GC–MS), matrix-assisted laser desorption coupled to time-of-flight mass spectrometry (MALDI-TOF-MS), and LC–MSn to investigate the potential volatile and non-volatile migrants from packaging materials into food (4). Which polyester oligomers or other chemical compounds did you find in your migration assessments?
In this work the migration assays were analyzed using LC–MSn, only positive mode was considered and ethanol (95%) was used as the simulant because it is well-known to be the one solvent that represents the worst scenario regarding oligomers migration. Moreover, it was necessary to elaborate a homemade database of possible oligomers considering the more common starting substances used in the fabrication of polyester coatings (polyacids and polyols) and combine linear and fully cyclized forms. Using this method, it was possible to identify in the simulant, for example, cycle oligomers of 2PA+2NPG (oligomer formed by two molecules of phthalic acid and two molecules of neopentyl glycol, Cramer class III) and 3PA+3NPG, found in the three samples used in this study. It was also noted that 2PA+NPG+HD (oligomer resulting from two molecules of 1,6-hexanediol, Cramer class III) and 2PA+2HD were found only in one sample. In addition, caprolactone cyclic oligomers were identified. Some of these compounds have also been reported by other authors. More of the oligomers were cyclic, probably because they are unreactive byproducts that are not incorporated into the polymeric network of the coating.
What are your greatest analytical challenges for accurate and precise analysis of PFAS materials in environmental samples?
One thing that worries me and also other researchers working with persistent pollutants in environmental and food samples is the presence of these compounds in the analytical equipment. In the particular case of PFAS, some supposed inert materials used in the liquid chromatograph tubing and fittings can be the source of contaminant chromatography peaks; especially if a very sensitive mass spectrometer is used. These contaminants can interfere with the very low limits of detection that could be achieved without contamination.
For you, what are the most important questions to answer or an important problem still to solve related to PFAS contamination?
In my opinion the most important question is do we know which PFAS are in the food contact materials? Alternatively, are we only realizing a small part of a bigger issue? The chemical complexity of PFAS implies that, unfortunately, we will probably be discussing and investigating PFAS contamination for several more years.
What can you share with our readers regarding your next area of interest for your research?
The greatest concern that exists (totally justified) about the environment and the high amounts of plastic materials that are used today, is that new materials (biobased, biodegradable, compostable, recyclable and so on) are being used for food contact applications. Obviously, these environmentally friendly materials are very important to maintain our planet’s environment, but we cannot forget that these materials must be safe for consumers. With each new material that appears in use for food contact, new safety issues can occur if special care is not taken during its manufacture. With this in mind we are certain that new research from the food contact safety point of view will still be needed.
(1) A.R.B. de Quirós, A.L. Cardama, R. Sendón, and V.G. Ibarra, Food contamination by packaging: Migration of chemicals from food contact materials (Walter de Gruyter GmbH & Co KG, 2019). ISBN-10: 3110644878
(2) V.G. Ibarra, A.R.B. De Quirós, P.P. Losada, R. and Sendón, Non-target analysis of intentionally and non-intentionally added substances from plastic packaging materials and their migration into food simulants. Food Packaging and Shelf Life, 21, 100325 (2019). https://doi.org/10.1016/j.fpsl.2019.100325
(3) A. Lestido-Cardama, R. Sendón, J. Bustos, M.I. Santillana, P.P. Losada, and A.R.B. de Quirós, Multi-analyte method for the quantification of bisphenol related compounds in canned food samples and exposure assessment of the Spanish adult population. Food Packaging and Shelf Life, 28, 100671 (2021). https://doi.org/10.1016/j.fpsl.2021.100671
(4) A. Lestido-Cardama, P. Vázquez-Loureiro, R. Sendón, J. Bustos, M.I. Santillana, P. Paseiro Losada, and A. Rodríguez Bernaldo de Quirós, Characterization of Polyester Coatings Intended for Food Contact by Different Analytical Techniques and Migration Testing by LC-MSn. Polymers, 14(3), 487 (2022). https://doi.org/10.3390/polym14030487