An optimized procedure for extraction and identification of microplastics in marine sediment

Microplastics (MPs) in sediment environments have been widely reported. As the number of samples increases, establishing a reliable and effective method becomes increasingly urgent for the rapid extraction and identification of MPs in sediments. Herein, we proposed a system with continuous density flotation of NaBr-ZnCl₂ (mixture of NaBr and ZnCl₂) solution for extracting MPs in a sediment sample, combined with micro-Fourier transform infrared (μ-FT-IR) imaging scanning for identification of MPs. The recoveries of MPs were estimated for four different sizes, shapes, and ten different types of polymers. The results indicated NaBr-ZnCl₂ solution showed a high recovery rate from 88.33% to 100.00% for extracting these different MPs. The μ-FT-IR imaging scanning allows for the detection of plastic down to the size of 6.25 μm in filed samples, and merely takes about 3 min, which was validated by testing of sediments from Jiaozhou Bay, China and its adjacent estuaries.