Two articles published on April 5, 2022, in the Journal of Agricultural and Food Chemistry, focus on the chemical analysis and identification of intentionally added substances (IAS, e.g., additives) and non-intentionally added substances (NIAS) contained in food contact materials (FCMs) and migrating from it. Especially the identification of NIAS, since mostly unknown, is challenging but essential to evaluate the safety of FCMs.
In their research article, Xue-Chao Song from the University of Zaragoza, Spain, and co-authors present a collision cross-section (CCS) database helping in the identification of chemicals in FCMs assessed by targeted and untargeted chemical analysis.
The method used in the study is based on travelling wave ion mobility spectrometry (TWIMS), which is a technique to separate and differentiate ions according to their mobility through a travelling wave in a gas (e.g., nitrogen) filled cell that can be coupled to mass spectrometry for a better separation and identification of small molecules including food contact chemicals (FCCs). From TWIMS, CCS values can be calculated. The CCS is a precise physicochemical property of an ion related to its chemical structure and 3D conformation. It can be used in addition to other ion parameters, such as exact mass, to increase the specificity of targeted and untargeted chemical analysis. The advantage of CCS measurements is that they are reproducible and unaffected by a sample matrix (e.g., food).
In February 2022, Song and colleagues already published a CCS prediction tool to identify NIAS in FCMs (FPF reported). The goal of their current study was to develop “a more comprehensive” traveling wave collision cross section in nitrogen (TWCCSN2) database containing both IAS and NIAS that migrated from FCMs under foreseeable conditions of use or that can be extracted with a solvent. The scientists measured 675 standard solutions over a period of two and a half years (November 2018 to July 2021) by ultrahigh performance liquid chromatography coupled to a quadrupole-time-of-flight mass spectrometer (UPLC-IMS-QToF) in positive and negative ionization modes.
In total, they detected 1038 ions that can be divided into 811 cations and 227 anions. The compounds include commonly used additives, such as plasticizers, antioxidants, and photoinitiators, as well as NIAS such as oligomers and additive degradation products. Bisphenols and per- and polyfluoroalkyl substances (PFAS) were also among the compounds detected in the negative ion mode. With an average CCS variation of < 1.1% over the two and a half years, the accuracy and reproducibility of the measurements was found to be high. The authors further compared their TWCCSN2 values with previously published CCS measurements and found “85.7, 87.7, and 64.9% [M + H]+, [M + Na]+, and [M − H]− adducts showed deviations <2%.” Potential reasons for some high deviations are also discussed in the article. Moreover, Song et al. compared their values with predicted CCS values from three different tools in the FCMs area and reported that the tool CCSondemand resulted in the most accurate predictions. According to the scientists, CCS prediction tools could aid in reducing false positives and help in tentative identification, but they could not “be used to confirm the identification of an unknown compound.”
The authors concluded that the TWCCSN2 values in their database “can serve as additional confirmation points for the identification of FCCs in targeted and untargeted screening analyses.”
Researchers of the same group have previously tested different techniques for oligomer detection and reported on the oligomers migrating from biopolymers (FPF reported) and from biodegradable teacups (FPF reported).
In another article, Raegyn B. Taylor and Yelena Sapozhnikova from the US Department of Agriculture, Agricultural Research Service, Wyndmoor, Pennsylvania, assessed the chemicals migrating from plastic FCMs into food simulants, also looking at unknowns. They purchased 24 food packaging samples including meat trays, cling wrap, as well as storage and vacuum bags in Philadelphia in 2019. They performed migration experiments on the samples according to the US Food and Drug Administration’s (FDA’s) guidance on food contact substances, and they analyzed the samples by nontargeted liquid and gas chromatography (LC and GC) high-resolutions mass spectrometry. For putative compound identification, the scientists compared their LC data against Chemspider, MzCloud, and HRAM Extractable and Leachable databases and their GC data against NIST MS (2017) and HRAM GC-Orbitrap libraries.
Taylor and Sapozhnikova putatively identified 90 migrants by LC and 17 by GC analysis. Furthermore, 14 hydrocarbons and siloxanes were semi-identified. While they found the overall abundance of migrating compounds to be consistent across analyzed samples, they reported that chemical levels differed between packaging types. For instance, in GC analysis, the highest differences were reported between meat trays. In addition, the researchers found that the degree of chemical migration varied over the 10 days the samples were leached. Comparison with the Food Packaging Forum’s (FPFs) databases of chemicals associated with plastic packaging (CPPdb, FPF reported) and intentionally used food contact chemicals (FCCdb) showed that 18 of the compounds tentatively identified are listed in the CPPdb and 37 in the FCCdb. In general, most of the compounds detected in the study were IAS, including dyes, coatings, and plasticizers, as well as several plastic slip agents while the researchers considered nine compounds to be NIAS.
In addition, Taylor and Sapozhnikova reported that “eleven putative migrants are listed as substances of potential concern or priority hazardous substances.” The authors further confirmed two compounds with analytical standards, one being the NIAS tris(2,4-di-tert-butylphenyl) phosphate (CAS 95906-11-9), an oxidation product of the antioxidant Irgafos 168 (CAS 31570-04-4), which they also semi-quantified. The compound’s migration levels “exceeded proposed theoretical maximum migration values.” The researchers hope that their data will help guide “future studies studying migration and prioritizing migrants that currently lack empirical toxicological data, a necessary tool for understanding the chemical risk of food packaging.”
References
Taylor, R. B. and Sapozhnikova, Y. (2022). “Assessing Chemical Migration from Plastic Food Packaging into Food Simulant by Gas and Liquid Chromatography with High-Resolution Mass Spectrometry.” Journal of Agricultural and Food Chemistry. DOI: 10.1021/acs.jafc.2c00736 8 (pdf)
Song, X.-C. et al (2022). “A Collision Cross Section Database for Extractables and Leachables from Food Contact Materials.” Journal of Agricultural and Food Chemistry. DOI: 1 0.1021/acs.jafc.2c00724
