Quantitative Detection of Microplastics in Water Through Real-Time Analysis of Fluorescence Signal

Worldwide great concern has recently arisen about pollution by Microplastics (MPs) as a new major and ubiquitous hazard for human health and ecosystems with undetermined, yet potentially dangerous effects. However, despite a great research effort, the methods for quantitative identification still rely on long and subjective visual counting procedures carried out on optical microscopes by skilled human operators. In this study, a new automatic, portable, low-cost, and fast method for the quantitative detection of MPs in water is presented. Based on a modified optical scheme of a confocal microscope, the system automatically processes and counts the fluorescence pulses emitted by dye-stained MPs in flowing liquids after excitation with a low-power laser beam. Absolute calibration and tests to determine particle counts as a function of the flow rate were performed with commercial fluorescent 10-μm polystyrene microbeads. The particle count was found to increase linearly as a function of the flow rate up to a value of 600 ml/h. Real sample measurements were performed on three different types of commercial bottled water samples. The result were in good agreement with microscope observations. Therefore, the present investigation demonstrated the proof of concept of a methodology for quick automated counting of MPs in water.