Toward accurate olefin quantification in plastic waste oils: Analytical strategies and future directions

The global production of plastic waste exceeds 400 million tons annually, driving interest in chemical recycling processes like pyrolysis and hydrothermal liquefaction. These technologies generate hydrocarbon-rich oils with high olefin content, offering valorization opportunities but also presenting challenges for storage stability and upgrading. Accurate quantification of olefins in these complex mixtures remains a major analytical bottleneck. This review critically examines established and emerging methods for olefin analysis, including titration, FTIR and NMR spectroscopy, chromatographic approaches (1D-GC, GC × GC, HPLC), and selective strategies such as silver-ion complexation, chemical derivatization, and low-energy ionization mass spectrometry. We emphasize the limitations of standardized techniques and the potential of advanced approaches, particularly GC × GC-VUV and soft ionization MS, for enhanced selectivity and sensitivity. Finally, we highlight persistent gaps in method validation, standardization, and isomer discrimination, and propose research directions to improve analytical accuracy, reproducibility, and applicability to the complex matrices found in plastic-derived oils.