Evaluating the influence of polystyrene standards on quantification in environmental samples

Mismanagement of plastic waste has become an emerging concern as large plastic items fragment into microplastics and nanoplastics (MNPs) in the environment, which, in turn pose potential environmental and human health risks. Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) is an emerging analytical method for MNPs in environmental matrices, but there are uncertainties in the analysis as it is an indirect technique. To date, studies on the impact of molecular weight and tacticity on pyrolysis product formation of polystyrene (PS) using Py-GC-MS are scarce. To provide more insight on potential limitations with the analysis of PS, this study investigated eleven PS standards with a wide range of molecular weights (1,400–1,080,000 g/mol) and tacticities (isotactic, atactic, and syndiotactic) to evaluate how pyrolysis product formation varies and impacts quantification. Isotactic and syndiotactic polystyrene produced higher relative amounts of dimer and trimer compared to atactic polystyrene, irrespective of molecular weight. Additionally, five standards, covering a range of tacticities and molecular weights (1,400–476,000 g/mol), were used to quantify the PS concentrations of commercial products and assess their impact on quantifying the correct masses. Overestimations were mainly observed when atactic polystyrene with low molecular weight (1,400 g/mol) was used to calculate the concentration of PS, while the concentrations calculated using standards above 250,000 g/mol were similar regardless of tacticity. Assessment of the formation of the different pyrolysis products also provided the first indication that 3 consumer products were comprised of acrylonitrile-butadiene-styrene (ABS), providing the opportunity for mis-identification as PS and the necessity of monitoring multiple PS pyrolysis products and their concentration ratios to assess for this. Therefore, it is critical to carefully select calibration standards and monitor pyrolysis products for the accurate quantification of PS in samples. ∙ Py-GC-MS analysis of polystyrene (PS) with different tacticity and Mw ∙ Eleven consumer products tested for reliability of reporting PS concentrations ∙ Significant overestimation when standard molecular weight < 250,000 g/mol ∙ Acrylonitrile-butadiene-styrene products provide false positive of PS in samples