Chemiluminescence system for automatic determination of chemical oxygen demand using flow injection analysis

A novel chemiluminescence (CL) system for automatic determination of chemical oxygen demand (COD) combined with flow injection analysis is proposed in this paper. In this system, potassium permanganate is reduced to Mn2+ which is first adsorbed on a strongly acid cation-exchange resin mini-column to be concentrated during chemical oxidation of the organic compounds at room temperature, while the excessive MnO4− passes through the mini-column to be waste, then the concentrated Mn2+ is eluted reversely and measured by the luminol–H2O2 CL system. The calibration graph is linear in the range of 4–4000 mg l−1 and the detection limit is 2 mg l−1. A complete analysis could be performed in 1.5 min including washing and sampling, giving a throughout of about 40 h−1. The relative standard deviation was 4.4% for 10 mg l−1 COD (n=11), 4.8% for 100 mg l−1 COD (n=11). This CL flow system for determination of COD is very simple, rapid and suitable for automatic and continuous analysis. The presented system has been applied successfully to the determination of COD of water samples.