Advancing pyrolysis-gas chromatography mass spectrometry for tire wear particle mass quantification: effects of elastomer type, microstructure, and sample preparation

Tire and road wear particles (TRWPs) are a major source of microplastic pollution, yet their accurate quantification by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) remains challenging due to variability in tire tread composition and pyrolysis marker performance. To better understand the sources of this variability, this study systematically investigates how elastomer type, microstructure, sample preparation, and calibration material influence pyrolysis marker formation and quantification accuracy. Using tread samples with known composition and pure elastomers (styrene butadiene rubber (SBR) variants, butadiene (BR), and natural rubber (NR)), single-marker approaches were compared against multi-marker strategies under varying pyrolysis and sample preparation conditions. Elastomer microstructure was identified as a major control on marker formation and accounted for 49% of the adjusted variation in marker response among tire tread formulations investigated. Single-marker quantification generally underestimated synthetic rubber (SBR + BR) content, with recoveries as low as 16%, whereas multi-marker sets improved accuracy. However, both approaches showed formulation-dependent bias, resulting in under- and overestimation across tire types. Marker yield was also influenced by sample preparation and physical state, with systematic differences observed between solvent-cast elastomers, pure elastomers, and vulcanized tire treads, indicating that calibration based on idealized reference polymers may not adequately represent real tire materials. Recovery testing in marine sediment demonstrated strong matrix effects, with untreated sediments causing substantial overestimation and multi-marker approaches providing more reliable quantification following sample pretreatment. Comparison with ISO-recommended methods highlights the limitations of universal calibration strategies. Our findings support harmonized multi-marker protocols, market-representative reference materials, and quantification approaches that explicitly account for tire heterogeneity to improve the robustness of TRWP measurements.