Chia seed-assisted separation and detection of polyvinyl chloride microplastics in water via gas chromatography mass spectrometry

Chia seeds were used to significantly improve the separation efficiency of polyvinyl chloride (PVC) microplastics from water samples via centrifugation. Upon hydration, the mucilage of chia seeds were able to capture PVC microplastics with sizes ranging from tens to hundreds of micrometers. Since PVC microplastics contained di-2-etylhexyl phthalate (DEHP) as a plasticizer (verified via Fourier transform infrared spectrometry), DEHP was used as an indicator in the subsequent quantification via gas chromatography - mass spectrometry (GC-MS) analysis. Specifically after verifying the DEHP peak in the GC spectrum using DEHP reference standard as a positive control, the GC spectral area of that peak was used to quantify the amount of DEHP in the sample. Using nominal operation settings at 10 min and 1000 rpm with 100 mg of chia seeds, the separation efficiency could be improved by 5 times (500%) as compared to the absence of chia seeds. Furthermore, chia seeds were also compatible with simulated synthetic wastewater samples. Most importantly, the use of chia seeds did not interfere with GC-MS quantification protocol and accuracy. The result suggested the proposed method can be used as a simple screening tool of microplastics entering wastewater treatment plant, even though a series of follow-up studies are needed in future.