Portable Pyrolysis-Microplasma Carbon Optical Emission Spectrometric Device for Detection of Micro- and Nanoplastics in Water

Plastics are like a double-edged sword, offering different properties to meet various demands of modern life, but they degrade into micro- and nanoplastics (MNPs), posing environmental and health risks. Despite growing interest in the quantification of MNPs, achieving on-site determination of MNPs in water samples remains challenging due to costly and cumbersome instrumentation. Herein, a simple method coupling a miniature point discharge optical emission spectrometer (μPD-OES) with a portable pyrolyzer (Pyr) was proposed to monitor the total MNP pollution. Total organic carbon (TOC) serves as the MNP quantification index. After sulfonation and Fenton digestion, MNPs and other particulate nonblack carbon organic matter were removed, leaving only particulate black carbon (PBC). MNPs and PBC are collected via potassium peroxodisulfate oxidation and Fenton digestion. The TOC of MNPs can be calculated as the difference. After digestion, the collected MNPs were decomposed in the portable pyrolyzer to generate pyrolysis products, which were purged into a μPD-OES for the detection of carbon atomic emission lines. Under optimal conditions, the proposed method attained a detection limit of 0.43-8.56 μg C L^-1, with a precision (RSD, n = 11) better than 4.0%. The proposed method was successfully applied to detect MNPs in tap water, river water, seawater, domestic sewage, and industrial wastewater samples, and the results obtained were in good agreement with a commercial TOC analyzer, confirming that the method possesses sensitivity and accuracy and reduced need for costly, bulky instruments, while minimizing energy consumption, offering strong potential for rapid, sensitive, and precise MNPs monitoring.