Novel spectral comparison for chlorinated paraffin analysis using planar solid phase extraction coupled to high-resolution mass spectrometry

Separation of chlorinated paraffins (CP) from complex matrices is challenging and their accurate quantification lacks in reference substances. A reference standard-free approach was newly applied to combine planar solid phase extraction (pSPE), high-resolution mass spectrometry (HRMS), and a mathematical comparison between computed and observed isotopic patterns for the objective, data-driven evaluation of the CP composition. The dopant ammonium chloride enabled the sensitive and reproducible detection and assignment of CP congeners. This was demonstrated for two technical CP standard mixtures, in which 31 and 28 congeners were assigned with high consistency by flow injection analysis-ESI-HRMS and pSPE-ESI-HRMS, respectively. In spiked vegetable oils, the expected congener pattern was successfully recovered, confirming the applicability of pSPE-ESI-HRMS for complex sample analyses. Applicability to real samples was demonstrated for CP congeners detected in CP-contaminated vegetable oils. The differentiation between explainable and unexplained mass spectrometric signals provided an optional non-target analysis. To ensure reproducibility and transparency, an evaluation routine based on a mathematically defined spectral similarity score was implemented, allowing a clear criterion for congener assignment. For future quantification, hexabromocyclododecane was evaluated as a suitable internal standard. The developed method enables an objective, reproducible, and accreditation-oriented approach suitable for automated evaluation for CP assignment without reference standards.