An environment-friendly device for rapid determination of chemical oxygen demand in waters based on ozone-induced chemiluminescence technology

Abstract

An environment-friendly device based on ozone-induced chemiluminescence (CL) technology was developed and optimized for the rapid measurement of chemical oxygen demand (COD) in waters. The purpose of this paper was to introduce a system that could be used in the field and has the characteristics of simple operation and avoiding the use of chemical reagents. Moreover, no more than 3 mL was introduced into the CL cell by using a syringe and mixed with ozone gas flow that could be produced online using an electrolytic ozone generator, which could lead to generating CL immediately and then the weak emission was focused into a photomultiplier tube through a specially designed optical system. Although the measurement procedure is simple, the method was sensitive as sharp peaks appeared within seconds for milligrams of COD, and the lower limit of detection was 0.1 mg L⁻¹. The light intensity difference (ΔI) of the CL detection system between deionized water and real sample water was proportional to the COD value of the water sample. A complete analysis can be performed in 2 minutes including sample addition and signal processing. Compared with conventional methods, this method required a smaller volume of water sample (3 mL vs. 30 mL) and was less time-consuming (2 min vs. 2 h), and was free of chemical reagents. The correlation between the presented method and the conventional permanganate chemical oxygen demand (COD_Mn) for several real water samples showed a good determination coefficient R² = 0.9947. Owing to its characteristics of rapid, simple, sufficient sensitivity and low cost, this method provides a promising tool for large-scale environmental assessment and industrial process control.