Quantification Challenges in Polymer Analysis in Urban Runoff and Wastewater using Pressurized Liquid Extraction and Double-Shot Pyrolysis-Gas Chromatography-Mass Spectrometry

Microplastics are persistent environmental pollutants with potential risks to ecosystems and human health. This study optimized methods for isolating and quantifying polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS) in environmental water and wastewater samples using pressurized liquid extraction (PLE) combined with pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The optimized two-step PLE protocol, consisting of methanol pre-extraction at 100 °C followed by tetrahydrofuran (THF) at 180 °C, achieved MP recoveries of 43-58%. Calibration curves were established using both solubilized and solid MP standards, with solubilized calibrations providing higher accuracy for PET and PP. Py-GC/MS conditions were optimized at 625 °C for 40 s to ensure maximum sensitivity and reproducibility. PE and PET were identified as the dominant MPs in the wastewater samples, with concentrations of 99.4 ± 71.8 μg/L and 16.2 ± 13.3 μg/L in Avedøre, and significantly higher levels of 749.0 ± 200.0 μg/L and 56.7 ± 22.6 μg/L in Pontedera. PP and PS were detected at lower concentrations, with PP ranging from 8.2 ± 4.2 μg/L to 16.9 ± 6.5 μg/L, and PS from 2.2 ± 1.5 μg/L to 8.4 ± 2.6 μg/L. Our results highlight the challenges of MP analysis in water samples, emphasizing the impact of key method parameters (e.g., MP isolation, pyrolysis, and calibration) on analytical reliability. The proposed method enhances MP detection in different water matrices, offering a reliable approach for routine environmental monitoring. Future efforts should focus on refining protocols to improve accuracy and precision and advancing standardization to ensure consistent and accurate MP quantification.