qualitatively measuring the safety of biodegradable plastic eating utensils abstract this project...

Qualitatively Measuring the Safety of Biodegradable Plastic Eating Utensils

Abstract

This project demonstrated the safety of biodegradable eating utensils when exposed to high temperature, acidic conditions, which are commonly associated with many foods. Sample biodegradable eating utensils, composed primarily of polypropylene (73%), were exposed to various food acids at high temperatures (~75-80 OC). Using gas chromatography (GC-FID), the resulting solutions were tested for possible leaching of the propylene monomer (C3H6) from the exposed eating utensil. If propylene is to be found to in the solution , then biodegradable eating utensils would be dangerous to use for hot foods, as the propylene can be harmful if ingested. Fortunately, it was found that none of the resulting solutions contained any significant trace of propylene, and it can be concluded that biodegradable eating utensils are safe to use for all foods.

References

1. Biodegradable Forks, Eating Utensils • Plastic Cutlery ComposGraph ." BIODEGRADABLE Products, ComposGraph GREEN Paper Products. N.p., n.d. <http://greenpaperproducts.com/biodegradable-forks.aspx>.

2. "Gas Chromatography." CU Boulder Organic Chemistry Undergraduate Courses. N.p., n.d. <http://orgchem.colorado.edu/hndbksupport/GC/GC.html>.

3. Tsuji, Hideto. Degradation of poly (lactide)--based biodegradable materials . New York: Nova Science Publishers, 2008. Print.

4. "Twelve Principles of Green Chemistry | Green Chemistry | US EPA." US Environmental Protection Agency. N.p., n.d.

Introduction

Biodegradable plastics have been more frequently used due to the global concern for the environment and the popular, ongoing green initiative. These plastics are designed to decompose in both aerobic and anaerobic environments, meaning they can be composted or placed in landfills for further degradation. They are metabolized by microorganisms that can convert the plastic into a soil-like product that is eco-friendly. Biodegradable eating utensils are either based off of raw materials or petroleum, depending on the vendor.

Perhaps one of the most common examples of biodegradable plastic is in the form of eating utensils, which are molded from these plastics and produced on a large scale. These utensils are also partially made of potato starch. Schools and other facilities across the nation are widely providing these utensils for people to use with their meals. However, these utensils are used to eat foods that include extremely high temperature soups, stews, chili, grilled meats, and other hot prepared food. Due to the more fragile properties of these utensils, it may be possible that people are possibly ingesting small amounts of these plastics unknowingly, which could be a chronic health hazard to many. Ingestion of propylene may disrupt the endocrine system, and may lead to a range of cancers including prostate cancer. It is important to know whether or not these utensils can withstand common conditions associated with various foods may have, and to ensure the health safety for all people using these utensils.

Concrete results of successful detection are made possible through the use of GC-FID (Gas Chromatography - Flame Ionization Detector). GC-FID works by anaerobically decomposing organic solutions at high temperature to produce ions and electrons for detection. The ions come from a hydrogen flame inside the gas chromatographer, which then are detected using a positive and negative electrode to create a potential difference, sensitive to mass rather than concentration. The current induced by the ions hitting the detector is measured versus time. Solutions of heated food acids exposed to biodegradable eating utensils can be tested for propylene by comparing their gas chromatograms to that of a propylene standard, particularly retention times. By matching the peaks exhibited by each solution, a qualitative conclusion to determine whether or not propylene is present in a solution can be made.

Results and Observations

According to the gas chromatograms of each of the aqueous acidic solutions, no concrete detection of propylene was found. None of the peaks were found to have a similar retention time to that of the propylene standard. The observation that the physical properties of the utensil did not visibly or significantly change after exposure to the aqueous solutions agreed with these results.

The fact that propylene was not found to leach into the acidic solutions could be due to multiple factors. One would be the physical properties of polypropylene. Since the utensils are manufactured at temperatures much greater than that of which foods are commonly served (~400 OF), they should have high thermal resistance to leaching. In addition, polypropylene is a string of nonpolar hydrocarbons that does not dissolve well in polar, acidic solutions. Polypropylene is best dissolved in nonpolar solvents, such as hexane, which are generally very uncommon when speaking of conditions associated with foods. The combination of these properties make biodegradable eating utensils safe to use when consuming foods.

These findings are consistent with the safety claims that the biodegradable plastic company, Taterware, makes for their products on their website.

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Future research would involve examining other components of the eating utensils, such as the potato starch. Other applications would include advancing and optimizing the biodegradable process of these plastic utensils to be composted and placed back into the environment in a harmless manner. One area of research could focus on reducing the amount of time these plastics need to be digested by microorganisms. Another potential application would be to develop safe eating utensils that can act as a fertilizer upon quick decomposition in soil, as to pose no threat to ecosystems and to improve soil quality.

Discussion and Conclusions

Acknowledgements

We would like to give special thanks to our Graduate Student Instructor, Aaron Harrison, for guiding us with our project and answering any questions we had. We would also like to thank Professor Jamie Cate for offering us suggestions on how to build on our project idea.

Special thanks is also given to Will Tooney and all the Chemistry 4 stockroom assistants, who helped supply all the materials required for this project, and also for showing us how to use the lab instruments for our data collection.

Experimental Procedure

Preparation of Various Acidic Solutions

One biodegradable plastic eating utensil (~9.5 g, Taterware) was immersed in each 30 mL acidic solution and then heated for 45 minutes at 75-80 OC. The solutions were then cooled to room temperature and the plastic utensils were removed from solution. The aqueous solutions were then placed in gas chromatography vials for analysis.

Gas Chromatography- Flame Ionization Detector (GC-FID)

Data

Graph 2: Acetic Acid

Retention Time of Peak Voltage (min) 1.433

Peak Voltage (V) 0.33

Peak Area (Counts) 730872

Graph 5: Phosporic Acid




Graph 1: Propylene Standard




Graph 4: Oxalic Acid




10 mL of acetic, phosphoric, lactic, oxalic, and citric acid were each added to 90 mL of distilled water. 30 mL of each of these aqueous solutions were added to 50 mL beakers to be exposed to the biodegradable eating utensils. A propylene standard was created by dissolving 0.15 g of solid polypropylene in 30 mL of hexane, which was then centrifuged and placed in a gas chromatography vial.

Graph 3: Lactic Acid




Graph 6: Citric Acid




A 1079 injector type was used. The method was set to 225 OC, with a run time of 3.39 minutes and a flow rate of 5 mL per minute. A 1 microliter injection of each solution was placed into the gas chromatographer and gas chromatograms were plotted, voltage versus time. Each peak was noted and its retention time was compared to the gas chromatogram of the propylene standard, to determine if any propylene is present in the solution.

Utensil Exposure

According to the propylene standard chromatogram (Graph 1), the peak corresponding to the propylene monomer was found to be at a retention time of 1.288 seconds, with an extremely high voltage of 10.89 volts. None of the tested aqueous acidic solutions showed a peak that corresponded well to that of propylene, the closest acids being acetic and citric acid with peaks at 1.433 and 1.359 seconds respectively (Graphs 2 and 6). In addition, none of these peaks had a voltage with any significant magnitude, all much less than 0.5 volts.

As far as observations, none of the biodegradable eating utensils had a visual change after their exposure to the heated acidic solutions. nor did they have any notable change in their overall mass. They remained consistent with their creamy white color and their shapes did not deform to any visible extent.

Image from Taterware website:

www.earth-to-go.com/taterware/faq

qualitatively measuring the safety of biodegradable plastic eating utensils abstract this project...

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