Tracking Chemical Migration in Reusable Plastic Bottles with LC–HRMS: An Interview with Selina Tisler

The challenge with estimating the chemical hazards of drinking water stored in reusable plastic bottles is due to numerous intentionally and unintentionally added chemicals in the plastic. Researchers from the University of Copenhagen (Denmark) have developed a broad screening strategy using evaporation enrichment and liquid chromatography high-resolution mass spectrometry (LC–HRMS) to evaluate migration of non-volatile chemicals from various reusable plastic bottles. Those involved with the study believe that their findings stress that comprehensive assessments of plastic materials are required to improve consumer safety. LCGC International spoke to Selina Tisler, corresponding author of a paper resulting from the research, about this strategy.

In your paper (1), you state that estimating the chemical hazards of drinking water stored in reusable plastic bottles is challenging due to the numerous intentionally and unintentionally added chemicals. Can you give us an idea of just how many chemicals we encounter when using these reusable plastic products?

We analyzed compounds using one chromatographic platform, liquid chromatography (LC), which does not capture very volatile compounds. Even with this limitation, we found that water stored for more than 24 hours can contain several hundred leached compounds for one of the worst-performing bottles. It is estimated that up to 100 times more compounds could potentially migrate into the water compared to those already present in drinking water (2), which is strictly regulated, unlike the materials used for the bottles.

What sort of health threats are in play, both short and long term?

We still lack a full understanding of the health risks, as most of the identified compounds were unknown or poorly studied. While bisphenol A (BPA) is well-known for its health risks and has been avoided by producers—we confirmed its absence in the bottles we tested—there is concern that similar compounds with comparable properties and potential hazards could be introduced as substitutes. These alternatives can still be marketed as 'BPA-free,' leaving consumers unaware of possible risks. For example, in two types of bottles, we detected Bisphenol A-diglycidyl ether (BADGE) derivatives, with unclear health effects.

Would you be able to comment on the difference in chemicals leaching from non-reusable plastic water bottles vs. reusable plastic water bottles?

We have not conducted a detailed investigation of non-reusable plastic bottles. However, in a pre-study with three types of PET bottles, we observed that only a very small number of compounds migrated into the water from intentionally single-use plastic bottles.

How much of a factor is the durability of a plastic bottle as opposed to a bottle you toss away after you finish the contents?

Durability is important particularly in terms of sustainability, and it should also have a positive environmental impact. However, the question remains whether plastic as material is always necessary or if it could also be glass or metal. In some cases, such as for biking, plastic may be unavoidable. We found that some plastic materials contained surprisingly low levels of chemicals and could be more suitable for applications where durability and flexibility is priority.

Your research aimed to develop a comprehensive strategy for evaluating the chemical migration from various reusable plastic bottles, utilizing vacuum evaporation concentration (VEC) enrichment combined with LC–HRMS analysis. What influenced you to use these techniques?

We conducted an initial study using liquid chromatography (LC), which demonstrated its effectiveness as a platform for identifying a wide range of chemicals leaching from plastic bottles into water (3). In the previous study, we employed solid-phase extraction (SPE) for sample enrichment, which offers the advantage of higher enrichment factors and, consequently, improved sensitivity. However, since SPE cartridges are made of plastic, they can introduce compounds into the analysis that are not present in the original sample. In contrast, VEC is a cleaner method, as it simply evaporates the water to concentrate the compounds. However, VEC also enriches salts and other matrix components, making the sample more complex and limiting the level of enrichment compared to SPE.

What are the key findings of your work?

Our study revealed that over 70% of approximately 1,000 unidentified compounds were unique to specific plastic bottles. This finding highlights the limitations of monitoring only target compounds, given the high diversity of chemicals used in plastic production. Among the bottles tested, silicone, high-density polyethylene (HDPE), low-density polyethylene (LDPE), and polypropylene (PP) showed the largest number of compounds migrating into drinking water. Especially the silicone bottles released a high number of unknown compounds, including phthalates and plasticizers. In contrast, polystyrene (PS), polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), and polycyclohexylenedimethylene terephthalate glycol (PCTG) bottles exhibited minimal migration, suggesting that they pose a lower health risk.

Were there any unexpected results during your research that required you to change your approach?

We faced challenges due to limited databases for identifying relevant compounds. However, ongoing efforts, such as studies from Wiesinger and coauthors (4) and the Food Packaging Forum's (FPF) database (5), are making significant progress in addressing this issue.

How did you analyze the data once you secured it?

We analyzed the data using the open-access software MSDial for initial compound screening. Following this, we conducted several manual steps, including extensive literature research, to confirm the tentative identification of the compounds.

How can your results be applied?

Our results provide a workflow for assessing the potential hazard of reusable plastic bottles in a way that is highly relevant to real-world consumer use, as we utilized real drinking water instead of food simulants. This approach can help manufacturers evaluate the safety of their materials more comprehensively. Additionally, by employing non-target screening, our findings highlight a broader range of migrating compounds, not just regulated substances like BPA, which could inform regulatory updates.

What are the broader implications?

Our study could raise awareness about the plastic materials used for food storage, encouraging consumers to carefully consider which materials best suit their needs. We also hope it inspires increased research funding and further studies in this field to better understand and mitigate potential risks.

What sampling and analytical challenges did you face?

We were surprised at how few challenges we encountered—triplicates of the same type of bottles showed very consistent leaching results in a simple setup of storing drinking water in the bottles. However, we only investigated the bottles themselves; analyzing the lids in a similarly consumer-representative way would likely be more challenging. Another limitation was the potential exclusion of relevant compounds during data filtering, as we were strict about removing any compounds that could have been introduced through plastic materials used in laboratory sample preparation and analysis.

Were there any factors that might affect the accuracy of your findings?

Blank filtering was an important step to ensure our results were accurate. We included 16 blanks stored in glass bottles and processed them the same way as the plastic bottle samples to check for any contamination. In addition, although we followed several quality assurance steps in our non-target screening, we cannot be sure about the exact concentrations of many of the leached compounds because analytical standards for these substances are not available.

Do you think your methods could translate in testing other plastic food container types?

Yes, our workflow could generally be applied to testing other types of plastic food containers. However, it would be important to select a representative matrix and adapt the sample preparation process to reflect how those containers are actually used.

What are your next steps in this research?

We are currently working on several projects focused on the quality of water using non-target screening. These do not involve food packaging materials. We hope to secure funding soon to expand our research in this area and continue exploring the impact of packaging on water quality.

References

1. Tisler, S.; Kristiansen, N.; Christensen, J. H. Chemical Migration from Reusable Plastic Bottles: Silicone, Polyethylene, and Polypropylene Show Highest Hazard Potential in LC-HRMS Analysis. J. Hazard Mater. 2024, 480, 136391. DOI: 10.1016/j.jhazmat.2024.136391

2. Grob, K.; Biedermann, M.; Scherbaum, E.; Roth, M.; Rieger, K. Food Contamination with Organic Materials in Perspective: Packaging Materials as the Largest and Least Controlled Source? A View Focusing on the European Situation. Crit. Rev. Food Sci. Nutr. 2006, 46 (7), 529–535. DOI: DOI: 10.1080/10408390500295490

3. Tisler, S.; Christensen, J. H. Non-Target Screening for the Identification of Migrating Compounds from Reusable Plastic Bottles into Drinking Water. J. Hazardous Mater. 2022, 429, 128331 DOI: 10.1016/j.jhazmat.2022.128331

4. Wiesinger, H.; Wang, Z.; Hellweg, S. Deep Dive into Plastic Monomers, Additives, and Processing Aids. Environ. Sci. Technol. 2021, 55 (13), 9339–9351.DOI: 10.1021/acs.est.1c00976

5. FPF. FCCmigex Database. https://foodpackagingforum.org/resources/databases/fccmigex(accessed 2024-12-10).

Selina Tisler is an Assistant Professor in the Analytical Chemistry Group in the Department of Plant and Environmental Science from University of Copenhagen. She received her PhD in Environmental Analytical Chemistry in 2019 from University of Tuebingen in Germany. She was a postdoc at Aarhus and Copenhagen University in Denmark from 2019-2022. Her research focus is the advanced analysis of water, especially non-target screening of compounds of emerging concerns (CECs) and their transformation products in the aquatic environment. Photo courtesy of Tinsler.