Simple-to-use and Portable Device for Free Chlorine Determination Based on MicrowaveAssisted Synthesized Carbon Dots and Smartphone Images

D. URIARTE; E. VIDAL; A CANALS; C.E DOMINI; M. GARRIDO

Roma

Conferencia; 2021 PortASAP Conference; 2021

COST Action PortASAP

A new portable and simple 3D printed device (Fig. 1) was designed for free chlorine determination in water samples. Chlorination is one of the most widely used disinfection processes because it is simple and inexpensive [1]. However, chlorine must be used with care, as it can react with naturally occurring organic species to produce different disinfection byproducts (DBPs), with trihalomethanes (THMs) and haloacetic acids (HAAs) being the main DBPs, which are considered as carcinogenic [2]. According to the WHO, control of DBPs could be achieved through monitoring precursor compounds, for which the determination of chlorine residues in drinking water is of real importance [1]. The free residual chlorine is defined as the sum of dissolved Cl2, HClO and ClO−, and it is normally expressed as mass of Cl2 by liter (mg L-1 or ppm) [3]. The analytical method was based on the quenching caused by free chlorine on the fluorescence emission of the carbon dots (CD) synthesized from citric acid and urea. The fluorescence was captured through the camera of a smartphone, which was coupled to the 3D printed device, and the images were processed using the RGB system by the ImageJ 1.51q software. The proposed method was selective and precise (RSD% 4.6, for n = 6), and the trueness of the results was evaluated by comparing the results obtained with those recovered by the spectrophotometric method 4500-Cl G (standard method) [4], with good agreement between them. Moreover, the remarkable correlation between the CD signal and the free chlorine concentration resulted in a determination with low detection limits (limit of detection of 6 µgL-1 and limit of quantification of 20 µgL-1). Therefore, the new method and the related portable device could be considered a fast, economical and reliable alternative for the on-site determination of free chlorine in water samples.Fig. 1. Scheme showing the different components of the portable device.AcknowledgementsThe authors wish to thank the financial support received from Universidad Nacional del Sur (PGI 24/Q099 and 24/Q086) and the ANPCyT (PICT-201-0659). The authors also thank Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) particularly for the doctoral grant of D. Uriarte.References[1] World Health Organization, Guidelines for Drinking-water Quality: Fourth edition incorporating the first addendum, Forth, 2017. [2] A. Mehta, H. Shekhar, S.H. Hyun, S. Hong, H.J. Cho, A micromachined electrochemical sensor for free chlorine monitoring in drinking water, Water Sci. Technol. 53 (2006) 403?410. [3] Federal-Provincial-Territorial Committee on Drinking Water, Guidelines for Canadian Drinking Water Quality Guideline Technical Document - Chlorine (Health Canada, Ottawa, 2009), pp. 1?39.[4] American Public Health Association. Standard methods for the examination of water and wastewater, 17th ed. Washington, DC, 1989:4-454-67