Quantification of polyethylene microplastics in liquid samples: preliminary results using nile red and Imagej analysis

Abstract

Microplastics have become a global pollution issue due to their presence in several ecosystems such as oceans, coasts, rivers, and lakes, among others. However, there is no standardized protocol for detecting and quantifying microplastics in liquid samples; but also, most quantification methods rely on visual counting of microplastics suspended in a solid medium, typically filter paper. This study presents preliminary results of microplastic quantification in liquid samples through image analysis using ImageJ software and different threshold values. Polyethylene microplastic in liquid samples were prepared in the laboratory using virgin polyethylene microplastics dyed with Nile red, 1 µg mL-1, and HPLC-grade water. The statistical analysis of the results performed using the Anderson-Darling normality test in Minitab® software, version 18.1, shows that this protocol is reliable for concentrations of up to 16 microplastics, with a 95% confidence interval. These results demonstrate the reliability of the proposed method for the quantification of microplastics in liquid samples.