Organochloride Speciation in Plastic Pyrolysis Oil by GC × GC Coupled to High-Resolution TOF-MS Using Scripting Expressions

The presence of chlorine (Cl) species in plastic pyrolysis oil (PPO) poses environmental and technical challenges for plastic recycling, including corrosion, catalyst deactivation, and the formation of undesired compounds during further processing of PPOs. Therefore, identifying and quantifying Cl-species is crucial to achieve PPO decontamination or avoid forming these molecules during the pyrolysis process. In this framework, a nontargeted screening methodology was developed, validated with Cl-standards spiked in a hydrocarbon mixture, and applied to a PPO sample by using comprehensive two-dimensional gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC × GC-HR-TOFMS). First, three filters were developed using scripting expressions based on exact mass differences and abundance ratios of chlorinated isotopic patterns. A strict filter permitted Cl-species detection without any false positives, but excluded a few Cl-species. Broader filters allowed the identification of additional chlorinated species, although they also brought a consequent number of false positives. Second, GC × GC-HR-TOFMS data were processed with the spectral analysis tools (SAT), an additional toolkit paired with the Leco ChromaTOF software, which helped identify MS fragments containing chlorine. SAT proved to be particularly effective in reviewing the list of potential Cl-species detected by the scripting expressions, enabling the distinction between false positives and chlorinated fragments. Screening Cl-species with filters and SAT allowed the identification of 24 organochlorides in a real PPO sample. Therefore, applying the described methodology has improved the analysis of PPO samples using GC × GC-HR-TOFMS, making the process faster and more powerful.