Differentiation of different subtypes of polystyrene microplastics using Nile red

Different subtypes of polystyrene microplastics (PS MPs) have shown distinct environmental behavior and different toxicity. The differentiation of different subtypes of PS MPs is highly desired but remains unachieved to date. Herein, we used the fluorescent dye Nile red (NR) to label different subtypes of PS MPs (general purpose polystyrene (GPPS), high impact polystyrene (HIPS), expandable polystyrene (EPS), carboxylated polystyrene (PS-COOH) and aminated polystyrene (PS-NH₂)) with predetermined dye concentration and dyeing temperature. Based on different dyeing efficiencies, five subtypes of PS MPs were differentiated in a short time by a fluorescence imaging method. The effects of various factors on the dyeing efficiency were also explored. Finally, this method was successfully applied to differentiate different subtypes of PS MPs in beach sand samples. This work pioneers the differentiation of different subtypes of PS MPs in the environment.