Decoding Chlorine Contaminants in Plastic-Derived Pyrolysis Oils with Chlorine-Selective GC×GC-AED

Chlorine contaminants in postconsumer plastic pyrolysis oils are a major bottleneck to their further valorization in the steam cracking process, where typical feed specifications require less than 3 ppm of chlorine. Current chromatographic approaches lack sufficient elemental selectivity and compound-independent quantification for complex pyrolysis matrices. Here, we present the first chlorine-selective, quantitative, comprehensive two-dimensional gas chromatography method with atomic emission detection (GC×GC-AED) for the analysis of complex pyrolysis oils. AED parameters were systematically optimized for maximum selectivity and sensitivity to chlorine. AED exhibited a largely compound-independent response with <5% variability relative to the internal standard, 3-chlorothiophene, across 28 representative model compounds. This comprehensive technique enabled the selective detection and quantification of chlorine-containing compounds in five distinct pyrolysis oils derived from real polyvinyl chloride (PVC) waste and two from mixed plastic waste rich in polyolefins. Using this approach, 85-99% of detected chlorine compounds could be tentatively identified, and GC×GC-AED provided chlorine concentrations for each compound. The total chlorine content determined by combustion microcoulometry, X-ray fluorescence (XRF), and GC×GC-AED showed close agreement (<5% relative variation), highlighting the comprehensiveness and analytical reliability of the optimized AED method. This capability establishes GC×GC-AED as a powerful tool for understanding chlorine transformation pathways and for improving dechlorination strategies in waste-plastic valorization by mapping chlorine's fate throughout the process.