Separation of microplastics from river water in a rotating spiral column using a water-oil system

Determination of microplastic content in natural waters is an urgent task in assessing the degree of pollution of water bodies, identifying sources of pollution, as well as in assessing potential risks for inhabitants of aquatic ecosystems and water consumers. The solution of such a problem mainly lies in the field of analytical chemistry, with particle separation methods playing the most important role. The present work shows for the first time the possibility of applying the method of flowing microplastic separation in a rotating spiral column using a water-oil system to assess the content of microplastics in river water. Microplastics in the extracted particle samples were determined by pyrolysis gas chromatography with mass spectrometric detection (Pyro-GC-MS). A water sample from the Moskva River was analyzed. Using the water-castor oil system, 1.8 mg/L of suspended solids were separated from river water. The decomposition procedure of the organic matter (30 % H2O2) of the sample reduced the mass of extracted particles to 0.4 mg/L. The residual fraction was studied by optical microscopy. According to the Pyro-GC-MS data, the total content of microplastics in the studied water sample was 109 µg/L, which is 1.4 % of the total suspended solids in the studied water sample. Five types of microplastics, namely polyethylene, polypropylene, acrylonitrile butadiene styrene, acrylonitrile butadiene rubber and polyethylene terephthalate, among which polyethylene is the main type (97 µg/l), were identified. The proposed method is promising for estimation of microplastic content in natural waters.