A simple chemiluminescence method for determination of chemical oxygen demand values in water

In this paper, a low cost chemiluminescence detector with a photodiode instead of photo-multiplier tube (PMT) was developed for environmental monitoring of water quality. Based on the chemiluminescent reaction of luminol-H₂O₂-Cr³⁺ system, light emission caused by luminol-H₂O₂-Cr³⁺ system was detected by the photodiode, and its intensity caused by the appearance of Cr³⁺ after samples digestion was proportional to the chemical oxygen demand (COD). Effects for COD determining such as pH, concentrations, interference, and digestion procedures were investigated. The experimental results show that this suggested method uses an instrument that is simpler and cheaper than the previous ones used for the same purpose. The data obtained by the present method were fairly in good agreement with those obtained by the standard reflux titrimetric method. It has been applied to determine real samples with satisfactory results.