RESUMO
An electrochemical analysis system for rapid determination of chemical oxygen demand ( COD) in flow state was established. A planar electrode modified with GO-NiNPs was matched with a 3D printed thin-layer cell. The sample was driven smoothly through the electrode surface by a micro peristaltic pump and then measured by chronoamperometry. The effect of modified materials, dielectric and electrochemical operating conditions were investigated. The whole response time of COD was 1. 5 min and the demand for the sample was about 2 mL. It turned out that the linear range of response in the low concentration region was 0. 15-100 mg/L, the linear equation was i(μA)=3. 974c (mg/L)+0. 2295 (r = 0. 9991) and the detection limit was 0. 04 mg/L. The linear response range in the high concentration region was 100-450 mg/L, and the linear equation was i(μA)=1. 938c (mg/L)+ 230. 9 (r = 0. 9877). Compared with the national standard method (GB11914-89) for measuring the actual water samples (Qinhuai River, Xuanwu Lake and Nanjing tap water), the correlation between them was quite good and the analysis time was dropped to 1/100. This new sensing system provided an environmentally friendly and portable method for detection of COD without using expensive, highly corrosive and toxic reagents.