Pyrolysis-GC/MS calibration for environmental quantification of tire tread: Standards and marketplace averaged elastomer subunit profiles

Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) enables quantification of tire and road wear particles (TRWP) in environmental matrices, but method refinements are needed to account for elastomer subunit variations. Environmentally distributed elastomers are a composite of formulations from many tire manufacturers, which can be represented by specially prepared reference materials. Thus, this study analyzed cryogenically milled tire tread (CMTT) composite materials blended from United States and European Union market-representative tire mixtures to determine operationally defined styrene (S_t) and 1,4-butadiene (B_t) monomer subunit content fractions in synthetic rubber (SR) fractions. Bootstrap resampling with least squares optimization revealed similar B_t (0.64-0.73) and S_t (0.06-0.09) contents across market composites, though precision decreased with larger particle sizes. Calibration polymer solutions stored at 4 °C maintained stability for three months, with response ratio changes below 15 %. Although alternative internal standards were evaluated, structural similarity between target and calibration polymers proved essential for complex environmental matrices, with up to 20 % quantitation differences observed when using dissimilar standards. This study demonstrates that market-representative composite CMTT materials provide operationally-defined elastomer subunit profiles that account for commercial variability in tire formulations. This approach enables accurate environmental TRWP quantification without requiring individual elastomer characterization.