In an article published on August 3, 2022, in the journal Food Chemistry, Asako Ozaki from the Osaka Institute of Public Health, Japan, and co-authors qualitatively and quantitatively evaluated the migration of volatile compounds from polyethylene terephthalate (PET) bottles.
For their experiments, they used 16 new non-recycled PET beverage bottles provided by the Japan PET Bottle Association including heat and non-heat resistant bottles from seven suppliers, as well as 21 commercially available PET water bottles purchased online and packaged in 11 countries. First, the scientists measured volatile compounds contained in the 16 new bottles using headspace gas chromatography coupled to mass spectrometry (HS-GC-MS). Subsequently, they performed short- and long-term migration experiments on eight of these bottles with distilled water and 50% ethanol at 25, 40, or 60°C and analyzed the samples for the previously identified compounds using purge-and-trap (PT-)GC-MS. The water in the commercially available PET bottles was also analyzed by PET-GC-MS after storage for 3, 6, 9, and 12 months at 25 °C.
Ozaki and co-authors identified six chemicals in the new PET bottles when comparing their chemical analysis results with the NIST-98 GC-MS library: acetaldehyde (CAS 75-07-0), 2-methyl-1,3-dioxolane (CAS 497-26-7), nonanal (CAS 124-19-6), decanal (CAS 112-31-2), benzaldehyde (CAS 100-52-7), and cyclopentanone (CAS 120-92-3). While acetaldehyde and nonanal were detected in almost all bottles, 2-methyl-1,3-dioxolane was mainly detected in the heat-resistant bottles. The latter compound was found to migrate in maximum amounts of 2.3 ng/mL and 19 ng/mL into distilled water and 50% ethanol, respectively, when stored for two years at 25 °C. Methyl-1,3-dioxolane was also detected in all waters stored in commercially available PET bottles in quantities between 0.03 and 3.1 ng/mL and nonanal in three bottles with quantities ranging from 0.54 to 1.8 ng/L. For both the new bottles and the commercially available bottles, chemical migration increased with the storage period. Ozaki et al. also estimated human exposure to 2-methyl-1,3-dioxolane based on the results of their long-term migration experiments and estimated soft drink consumption levels in Japan. They calculated the worst-case consumption “to be 15 times lower than the Threshold of Toxicological Concern.”
Besides intentionally added substances, also non-intentionally added substances (NIAS) can be present and migrate from plastics such as PET bottles. In an article published on July 23, 2022, in the journal Separations, Riccardo Aigotti and co-authors from the University of Turin, Italy, present an online method to quantify trace levels of NIAS migrating from PET food packaging. The authors applied an online solid-phase extraction (SPE) method to automate pre-concentration of the samples before an ultra-high-performance liquid chromatography (UHPLC) coupled to a mass spectrometry analyzer and assessed the sensitivity and selectivity of their developed method using 12 NIAS. Afterward, they tested the method on ten new PET bottles obtained from different Italian suppliers. To assess overall and specific migration, the researchers filled the bottles with the food simulants 3% acetic acid and 20% ethanol and heated them for 10 days to 60 °C.
Levels of detection (LOD) of the developed method were found to range from 0.002 µg/L for bisphenol S (BPS, CAS 80-05-7) to 13.6 g/L for 2,6-di-tert-butyl-4-methylphenol (BHT, CAS 128-37-0), while levels of quantification (LOQ) ranged from 0.01 g/L to 42.2 µg/L for the same two compounds. Based on these and the other assessed parameters, the authors concluded that “the sensitivity was high enough to detect, identify and quantify the analytes in samples, and the precision and accuracy of the lower limit of quantification guaranteed the quality of the results.” They suggest that “online SPE as an automated extraction procedure reduces systematic and random errors.”
Analyzing the new PET bottles for the 12 NIAS, the scientists detected bisphenol A, BPS, 4-cumylphenol, and octocrylene. Although the levels were found to be below the limits outlined in the European regulation for plastic food contact materials, the presence of NIAS in the samples motivated the authors to emphasize “the need for new regulation for these potentially toxic molecules.”
Also in 2022, an earlier report found unsafe levels of antimony in common beverages packaged in PET bottles (FPF reported), and a review on the topic showed that of 193 investigated chemicals, 150 have been measured to migrate from PET bottles (FPF reported).
References
Aigotti R. et al (2022). “Release of Selected Non-Intentionally Added Substances (NIAS) from PET Food Contact Materials: A New Online SPE-UHPLC-MS/MS Multiresidue Method.” Separations. DOI: 10.3390/separations9080188
Ozaki A. et al (2022). “Determination of potential volatile compounds in polyethylene terephthalate (PET) bottles and their short- and long-term migration into food simulants and soft drink.” Food Chemistry. DOI: 10.1016/j.foodchem.2022.133758
