Recent research by the Analytical Chemistry Group of the University of Valladolid (Spain) focused on determining nine plasticizers in honey samples by gas chromatography–mass spectrometry (GC–MS). While the team points out that there have been studies conducted previously focusing on the assessment of other contaminants in honey (such as metals, pesticides, antibiotics, and veterinary drugs), there are comparatively few that have been done specifically regarding plastics. LCGC International spoke to Silvia Valverde and Ana María Ares of this group about their research and the resulting article.
You mention in your paper (1) that there have been few studies focused on assessing the presence of plastic contaminants in honey in the past. Why do you think this is? Are there any that were especially inspirational in your research?
Despite plastics having been used for decades, our awareness of their pollution and widespread presence is relatively recent, as is our understanding of their adverse health effects. The studies conducted by Peñalver and associates (2), Kartalovic and co-authors (3), and Di Fiore and associates (4), served as inspiration for this research. These studies have played a crucial role in advancing research on the presence of contaminants, particularly plastics, in diverse environmental and food contexts, such as honey.
While it goes without saying that we shouldn’t want plasticizers in our honey, do their presence or other environmental chemicals affect the bee, the hive, or the honey in any way?
The presence of plasticizers and other pollutants in honey can negatively impact bees and the hive by weakening their immune systems and interfering with their behavior and reproduction patterns. This can lead to a decline in the beehive population. Additionally, these contaminants can compromise the quality and safety of honey for human consumption by altering its taste and potentially making it toxic. Therefore, it is essential to monitor and minimize honey contamination, as well as the factors exposed to bees.
Which plasticizers were the most prevalent, and what is their source in the environment?
The most prevalent plasticizers in our study, BBP (benzyl butyl phthalate), DEP (diethyl phthalate), and DEHA (di-2-ethylhexyl adipate), can reach honey through various environmental pathways:
i) Soil and water contamination. Plasticizers can seep into soil and water near sources of contamination, such as factories or landfills. Honeybees may collect contaminated water or nectar from plants growing in polluted soil.
ii) Contaminated air. Plasticizers can disperse in the air, and honeybees can encounter these contaminants during their flight and bring them back to the beehive.
iii) Deposition on plants. Plasticizers from air and water can settle on plants. Honeybees gather nectar and pollen from these plants, transferring contaminants into the honey.
iv) Use of contaminated products. Products containing plasticizers, like plastics in hive structures or agricultural practices nearby, can directly transfer these chemicals to honey through contact.
Why were gas chromatography (GC) and high performance liquid chromatography (HPLC) your techniques of choice in your analysis?
GC is particularly suitable for analyzing phthalates due to its ability to separate volatile organic compounds based on their vapor pressures. Phthalates, being volatile, can be effectively detected by GC at very low concentrations, which is critical for assessing contaminants in food products like honey, where even trace amounts matter. GC offers rapid analysis, facilitating high sample throughput, and ensures excellent quantitative accuracy, which is essential for precisely measuring phthalate levels in honey samples.
How are the analytical methods you selected and developed environmentally friendly or green in their approach?
An attempt has been made to develop an analytical methodology that is as environmentally friendly as possible by using ethyl acetate as an extractant, known as a green solvent, and employing minimal volumes (< 5 mL) of this solvent. The sustainability of this approach has been evaluated using several green analytical metrics, with the most significant drawback identified as the energy consumption of the gas chromatography-mass spectrometry (GC–MS) instrumentation, which is essential for these analyses and unavoidable.
Briefly state your findings in this study.
The study developed a novel analytical method using GC–MS to analyze nine plasticizers in honey samples. Efficient sample treatment involving dual solvent extraction with ethyl acetate and cleanup with florisil resulted in satisfactory analyte recoveries (77–118%). Chromatographic analysis on an Agilent HP-5MS column demonstrated quick analysis times (< 21 minutes) under optimized temperature conditions. The method was validated for selectivity, low limits of detection (0.1–3.1 µg/kg), quantification (0.2–10.3 µg/kg), linearity, matrix effect, trueness, and precision (relative standard deviation < 9%). Analysis of thirty samples from various sources revealed residues of five plasticizers in most samples. Importantly, health risk assessment based on detected levels indicated no significant risks to consumers.
You analyzed honeys from three different botanical origins (multifloral, rosemary, and heather). Were there any types of honey more susceptible to plasticizers or other environmental contaminants? Were there any other variables, like hive location, that influenced their presence?
This study, based on the analysis of 30 honey samples, provides initial insights that necessitate a more comprehensive investigation for conclusive results. Initial indications suggest that multifloral honeys might have higher concentrations of contaminants, while honeys sourced from local markets show potentially higher levels compared to those from experimental fields. However, no consistent pattern based on hive location has been discerned. As emphasized, a larger and more extensive study is required to draw definitive conclusions regarding the susceptibility of different honey types to plasticizer contaminants.
Do your findings correlate with what you had hypothesized?
The findings generally align with our hypotheses. We anticipated detecting plasticizer residues in honey samples due to potential environmental exposures. The efficient sample treatment method we developed allowed us to detect five specific plasticizers across various honey sources, confirming our expectations. However, the precise distribution and levels of these contaminants exceeded our initial predictions, highlighting the need for robust analytical methods to assess environmental and health-related impacts accurately.
Was there anything particularly unexpected that stands out from your perspective?
During the optimization of sample treatment, a strong matrix effect was observed across all three botanical origins evaluated, which could be effectively minimized with appropriate clean up steps. It was surprising to find that all origins exhibited a similar response to this matrix effect, a phenomenon not commonly observed with other contaminants studied. Regarding the results, it was unexpected to detect the presence of phthalates in all samples, specifically three of them, regardless of the type and origin of the honey.
Were there any limitations or challenges you encountered in your work?
In terms of challenges, analyzing phthalates presents a significant analytical hurdle due to their widespread presence in common laboratory materials. It requires meticulous cleaning of all equipment to ensure they are free from these contaminants, thus preventing false positives. Moreover, as previously mentioned, the limited number of samples analyzed underscores the need for a larger sample size to enhance the reliability of the conclusions drawn.
What best practices can you recommend in this type of analysis for both instrument parameters and data analysis?
Cleanliness in sample preparation, including rigorous cleaning of equipment and selecting efficient sample treatment methods, helps minimize contamination and ensure accurate measurements.
It is recommended to use statistical methods, such as calculating mean concentrations, standard deviations, and performing ANOVA, to effectively compare sample groups and identify significant differences. Additionally, employing visual tools like box plots is advised to illustrate data distribution and outliers, enhancing the interpretation of complex datasets, such as those from contaminant assessments in various types of honey.
Are there any other natural food crops that you think might benefit from this sort of analysis?
This analytical approach could be beneficial for assessing a wide range of natural food crops. It could be particularly valuable for crops exposed to environmental contaminants or those requiring strict quality control measures. Examples include fruits, vegetables, grains, and herbs often subjected to pesticides and heavy metals.
Can you please summarize the feedback that you have received from others regarding this work?
The project has sparked significant interest across various sectors of society, both within the scientific community and among the general public. This has led to its presentation at several international conferences and its coverage as a notable news story in Spanish newspapers.
Do you think more of this type of analysis should be performed on other natural foods?
Additionally, products like milk, meat, and seafood could also benefit from rigorous contaminant analysis to uphold food safety standards. Such comprehensive analyses are essential for ensuring consumer health and maintaining the integrity of food products worldwide.
What are the next steps in this research, and are you planning to be involved in improving this technology?
The next steps would involve expanding the study to clarify conclusions regarding the accumulation of plasticizers in honeys, exploring differences based on botanical and geographical origins, as well as packaging of the product.
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