Evaluation of some screening methods for the analysis of contaminants in recycled polyethylene terephthalate flakes

A range of different analytical techniques were used to test recycled polyethylene terephthalate (PET) flakes for potential chemical contaminants. The techniques used were headspace gas chromatography coupled to mass spectrometry (GC-MS), liquid extraction followed by GC-MS, supercritical-fluid extraction followed by GC-MS, and migration testing followed by elemental analysis using inductively coupled plasma mass spectroscopy (ICP-MS). The PET samples were 50 representative samples taken from 600 that had been collected throughout Europe and which had been screened for potential contaminants using a single technique of high-temperature GC-MS. Six of the 50 samples tested had been spiked with a selection of model contaminants, three samples were virgin PET flakes and two of the samples were from supercleaning processes. All samples were analysed 'blind' in this exercise. The qualitative results showed that most of the contaminants came from the first use, being flavour-aroma compounds from soft drinks. The quantitative analysis found concentrations under a few mg kg(-1) in the polymer, except for the spiked samples. Element migrations were low and only calcium, silicon and sodium had median migrations above 50 mug l(-1) . This in-depth analysis of recycled PET flakes did not identify any significant contaminants that had not already been detected by the high-temperature static GC-MS screening method, thus demonstrating its utility.