First Comprehensive Interlaboratory Assessment of Chemical Release Analysis from Recycled High-Density Polyethylene Pellets

Post-consumer recycled (PCR) plastics are increasingly used in sensitive applications such as cosmetic and home care packaging. However, their safe use requires a robust assessment of potentially releasable contaminants originating from previous use and recycling processes. Building on the work of CosPaTox (a European consortium of companies involved in cosmetic products and their packaging) and the PCR pellet analysis methodology developed therein, this study presents the first interlaboratory evaluation of chemical release analysis from recycled high-density polyethylene (rHDPE) pellets that provides insights into the different factors influencing reproducibility. Seven laboratories, belonging to different stakeholder groups within the supply chain of recycled plastics (brand owners, suppliers, and service labs), participated in a harmonized study in which pellets were extracted with 95% ethanol at 60 °C for seven days and subsequently analyzed by gas chromatography–mass spectrometry (GC-MS). Using a per-substance comparison approach, variability introduced at each stage of the analytical workflow was systematically assessed, including (1) extraction, (2) GC-MS analysis, and (3) chromatogram evaluation. The results show that differences in extraction and instrumental analysis are the main contributors to interlaboratory variability (median standard deviation between measurements climbing to ca. 26% and ca. 43%, respectively, vs. 12% in a single lab and on single equipment). Chromatogram evaluation was identified as a further source of variation (increasing median standard deviation to 52 to 55% versus ca. 43% if a single lab evaluated the chromatograms). As such, this study provides new insight into the reproducibility of GC-MS screening methods for recycled plastics and establishes a benchmark for variability in pellet-based safety assessments. The findings support the harmonization of analytical workflows and strengthen confidence in the safety evaluation of PCR materials.