Identification and quantification of volatile organic compounds in Chinese recycled HDPE: Consequences for its applicability

Abstract

Amidst the escalating plastic waste crisis, plastic packaging accounts for a large part. Recycling emerges as pivotal for mitigation. Ensuring the safety and quality of recycled plastics for packaging requires a thorough understanding of the characteristics and potential risks of contaminants that may be present. This study addressed challenges posed by excessive sample weight and polymer matrices affecting accurate quantification using headspace solid-phase micro-extraction (HS-SPME), optimizing a HS-SPME gas chromatography mass spectrometry method for comprehensive volatile compound characterization in polymers. An algorithm was developed to select suitable standards for semi-quantification based on structural similarity, enhancing quantification accuracy. We applied these methods to analyze 65 recycled high-density polyethylene (rHDPE) samples from diverse prior uses, identifying 362 volatile compounds. Notably, alkylbenzenes and alkylnaphthalenes emerge as predominant contaminants, likely stemming from detergent residues, with alkylbenzenes exhibiting higher intensities and alkylnaphthalenes posing elevated risk potentials. Benzophenone, chloroxylenol, and various phthalates were widespread, ranging in concentration from 1.3 to 9.5 mg/kg. Additionally, pesticides e.g., dimethazone and atrazine were found predominantly in samples from non-food bottles. Fragrances like D-limonene, texanol, and amberonne were frequently detected, with amberonne notably contributing significantly to off-odors in the recycled plastics. These findings underscore the complexity of rHDPE composition, highlight specific contaminants of concern, and provide references for improving the recycling process and ensuring the safety and adaptability of rHDPE for food contact purposes or other high value applications.