Analysis of Aldehydes, Benzene, and Limonene in Recycled Polyethylene Terephthalate

Significance of the Topic

Ensuring the safety and quality of recycled PET in food packaging requires monitoring of compounds such as acetaldehyde, benzene, and d-limonene that can migrate into contents. Residual acetaldehyde may affect flavor and odor, benzene is a known carcinogen, and limonene can influence taste profiles. Regulatory bodies set strict limits to protect consumer health.

Aims and Study Overview

The objective was to develop and validate an automated headspace GC/MS method using an Agilent 7697 headspace sampler coupled to an 8890 GC and 5977C MSD. The method targets quantification of acetaldehyde, benzene, and d-limonene in recycled PET, aiming for low detection limits, reliable calibration, and direct analysis of ground PET samples.

Methodology and Instrumentation

Samples were cryogenically ground PET pellets. Calibration standards were prepared via serial dilution covering 0.0245 to 600 ng/µL. A 20 mL headspace vial was loaded with 5 µL standard or PET sample. Key headspace settings included 120 °C incubation for 30 min and transfer line at 130 °C. The GC used a 60 m × 0.25 mm, 1.4 µm DB-VRX column with split 10:1 and helium at 1.0 mL/min. The MSD operated in SIM mode monitoring ions for acetaldehyde (42, 44), benzene (78, 77), and d-limonene (136, 68).

Key Results and Discussion

The method achieved excellent linearity over wide ranges with R2 values ≥0.999. LOD and LOQ were 0.034 and 0.112 ng/µL for acetaldehyde, 0.002 and 0.008 ng/µL for benzene, and 0.006 and 0.022 ng/µL for d-limonene. Retention times were 5.3, 8.4, and 11.1 min, respectively. Analysis of three recycled PET samples yielded acetaldehyde levels from 474 to 975 µg/kg, benzene from 5.5 to 18.6 µg/kg, and d-limonene from 0.42 to 3.21 µg/kg, demonstrating consistent detection across samples.

Benefits and Practical Applications

The fully automated headspace GC/MS workflow minimizes sample preparation and operator intervention. Rapid analysis and high sensitivity support routine quality control in recycling operations and verification of compliance with FDA and other regulatory standards for food-contact polymers.

Future Trends and Potential Applications

The approach could extend to other volatile or semi-volatile contaminants in recycled plastics. Integration with high-throughput screening and expanded spectral libraries will enhance monitoring of emerging risk compounds. Coupling with robotics and data analytics may further streamline industrial QC processes.

Conclusion

The developed method reliably quantifies trace levels of acetaldehyde, benzene, and d-limonene in recycled PET. Its sensitivity, linearity, and automation make it suitable for ensuring safety and quality of recycled food-contact materials.

Reference

1. Benyathiar P, Kumar P, Carpenter G, Brace J, Mishra DK. Polyethylene Terephthalate (PET) Bottle-to-Bottle Recycling for the Beverage Industry: a Review. Polymers. 2022;14(12):2366.
2. U.S. Food and Drug Administration. Use of Recycled Plastics in Food Packaging (Chemistry Considerations): Guidance for Industry. FDA; 2021.