Identification and quantification of microplastics in a wide range of aqueous matrices using pyrolysis-gas chromatography-mass spectrometry: method’s performance, greenness evaluation, and analysis of real samples

Abstract

This study describes the analysis of microplastics in aqueous matrices of varying complexity using pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC–MS). Depending on the filtration rate of the analysed matrix, sample treatment prior to Py-GC–MS consisted of filtration on 0.7 µm glass fibre membranes (low-complexity matrices), or microwave-assisted digestion of samples with hydrogen peroxide, followed by filtration as above-mentioned (high-complexity matrices). Low-complexity matrices included demineralised water (DMW), mineral water in polyethylene terephthalate (PET) bottles (BMW), drinking water from a public aqueduct (DW), and DW further treated with activated carbon and distributed in public fountains (FOW). High-complexity matrices included effluent wastewater from primary sedimentation (WW-PS), biological oxidation (WW-BO), clariflocculation (WW-CL), and quaternary treatment (WW-QT). Sample digestion significantly accelerated the filtration process of high-complexity matrices. In most cases, absolute value of matrix effect was <40 %, except for PET in WW-PS (-54 %) and WW-CL (-56 %), and polystyrene in WW-PS (75 %). Apparent recovery, studied in DMW, DW, and WW-BO matrices, was 90±24, 87±25, and 67±19, respectively. The methods were evaluated for their greenness, achieving scores higher than or comparable to those of previously published Py-GC–MS procedures. Poly(methyl methacrylate) and PET were never detected, while different levels of contamination were found for polystyrene, polyethylene, polypropylene, polycarbonate, polyamide, and polyvinyl chloride, depending on the sample type. The lowest contaminations were determined in BMW and DMW. FOW was more contaminated than DW (five microplastics detected at 2.7–138 µg/L vs. two microplastics detected at <0.62–23 µg/L) and concentrations in WWs were in the order WW-QT<WW-CL<WW-PS<<WW-BO.