In an article published on December 2, 2022, in the journal Environmental Science & Technology, Lei Wang and co-authors from the Shenzhen Campus of Sun Yat-sen University, Shenzhen, China, explored the occurrence and sources of organophosphate esters (OPEs) in a wide range of plastic and paper food contact materials in Southern China.
OPEs substitute brominated flame retardants and may also act as plasticizers. Their exposure has been linked to neurotoxicity and endocrine disruption (FPF reported). The Food Packaging Forum’s (FPF’s) October 2022 Fact Bite on OPEs illustrates that these flame retardants have already been detected in paper and board FCMs, plastics, multi-materials, and metals. They may originate from organophosphite antioxidants (OPAs) which are commonly added to polymeric materials to slow down aging and are naturally oxidized to OPEs.
Wang and co-authors analyzed 70 plastic and 30 paper FCMs that they purchased in supermarkets in South China. After emptying and washing the packaging with methanol, they extracted small pieces with 50:50 v/v hexane/acetone and applying them to 20 min ultrasonication, 10 min shaking, and 5 min centrifugation. Extracts were analyzed for OPEs as well OPAs by combining suspect screening and fragments-based nontarget screening using ultra-high-performance liquid chromatography (UHPLC) – high-resolution mass spectrometry (HRMS). Based on the peak area and the isotope dilution method, the scientists further (semi)quantified the detected compounds.
Wang et al. identified 21 OPEs over all smaples by comparison to a suspect list of 124 OPEs. 17 could be confirmed with authentic standards. In non-target screening, additional seven characteristic fragments of OPEs were identified which included four diaryl and three triaryl OPEs. Of the 28 OPEs, triphenyl phosphate (TPhP, CAS 115-86-6) and tris(2,4-di-tert-butylphenyl) phosphate (TDtBPP, CAS 31570-04-4) had the highest detection frequencies and were present in 97% of the samples. TDtBPP was also the OPE with the highest media concentration (<8.50−103,879 ng/g). Looking at OPAs, Wang and colleagues identified six OPAs in the FCM extracts. Concentrations of three OPAs showed a significant correlation with their corresponding OPEs, suggesting “that OPAs are an indirect source of their corresponding OPEs.” While “18 OPEs and 3 OPAs were found for the first time in the extracts of FCMs,”, seven OPEs and two OPAs were detected in >50 samples.
The researchers also compared the OPE and OPA concentrations between plastics and paper FCMs and reported that plastics contained a higher concentration of all analyzed compounds with the exemption of tributyl phosphate (TBP, CAS 126-73-8). To get an overview of OPEs/OPAs migration efficiency and actual human exposure to these compounds, Wang and co-authors performed migration experiments from a plastic coffee cup using different ethanol/water solutions (v/v: 0/100, 10/90, 30/70, and 50/50). UHPLC-HRMS analysis showed the presence of ten OPEs and one OPA in the food simulants. Migration efficiencies were reported to increase with the ethanol percentage and were highest for TBP with 15.4% migrating in 50% ethanol.
The authors concluded that a wide variety of OPEs and OPAs occur in FCMs available on the Chinese market and “that humans may be exposed to these OPEs and OPAs in the diet.” They expressed the need for future studies analyzing the occurrence of these OPEs and OPAs in foodstuffs.
A similar analysis was performed by another group of researchers from China In July 2022 that demonstrated the extensive contamination of Chinese foodstuff with OPEs and uncovered food packaging as a source of these OPEs (FPF reported).
While Wang et al. focused on organophosphit antioxidants, also phenolic antioxidants were recently found in FCMs. Wenjuan Zhu from Shenzhen Henan Normal University, China, and co-authors, investigated the migration of three of them, butylated hydroxytoluene (BHT, CAS 128-37-0), butyl hydroxyanisole (BHA, CAS 121-00-6) and tert-butyl hydroquinone (TBHQ, CAS 1948-33-0), from plastic FCMS into food simulants. In their article published on November 28, 2022, in the journal Food Chemistry, they described that BHT migrated from two of the five samples in amounts of 1.3-2.4 mg/kg. The main aim of the researchers was to develop “a green strategy for the detection of antioxidants in food simulants” which they detail in their publication and reported to be rapid and efficient.
References
Wang, L. et al. (2022). “Discovery of 18 Organophosphate Esters and 3 Organophosphite Antioxidants in Food Contact Materials Using Suspect and Nontarget Screening: Implications for Human Exposure.” Environmental Science & Technology. DOI: 10.1021/acs.est.2c05888
Zhu, W. et al. (2022). “A green extraction strategy for the detection of antioxidants in food simulants and beverages migrated from plastic packaging materials.” Food Chemistry. DOI: 10.1016/j.foodchem.2022.135060
