Rapid and Efficient GC-MS Method for the Multiresidue Analysis of Contaminants from Recycled Polyethylene and Polypropylene

In the context of plastic recycling, legislation is evolving and varies across regions, but it remains largely nonspecific. In the European context, producers of post-industrial and post-consumer recycled plastics must guarantee the same wholesomeness as virgin materials. However, they cannot maintain such strict control over incoming materials, because, since the secondary raw materials derived from separate waste collection, they are subjected to high variability in composition and heterogeneity over time. In this frame, a rapid, and easy-to-apply GC-MS method was developed. It employs a liquid-liquid extraction with acetone, followed by quantitative analysis with gas chromatography coupled to mass spectrometry (GC-MS). A combination of total ion chromatograms (TICs) and extracted ion chromatograms (EICs) was used. Adequate sensitivity was demonstrated in the selected concentration ranges for most of the analytes, with limits of quantification (LOQs) lower than the legislative limit, when existing. The results showed that the method is sufficiently accurate with recoveries ever higher than 68.3% and relative standard deviations (RSDr) smaller than 4.2%. This method allows, for the first time, the simultaneous quantification of 40 molecules at levels of a few ng/g. It ensures the possibility of obtaining real-time data for the production control system about the safety of the input materials, allowing immediate corrective action in the event of anomalies. This method is focused on PE and PP recycled plastics and is to be considered a screening method that allows for highlighting batches of incoming materials that are too contaminated to control the output material. This method was successfully tested analyzing some batches of plastics both in input and post-recycling.