عنوان مقاله [English]
In this research, potassium persulphate and hydrogen peroxide were investigated for their interference in the chemical oxygen demand (COD) test in the presence of reactive blue 19 dye. The chemical oxygen demand (COD)test is widely used for the estimation of the organic carbon content of water and wastewater. The test is prone to disturbance by such inorganic substances as nitrite, chloride, ferrous ion, and sulfide. The interference of chloride and nitrite may be prevented by adding mercuric sulfate and sulphamic acid, respectively. However, the interferences of persulphate and hydrogen peroxide are not mentioned in references. This research was carried out to show how persulphate and hydrogen peroxide interfere with the COD analysis. Results showed that samples containing various concentration of K2S2O8 and with no organic substances H2O2 had different COD values. It is recommended that the interference of persulphate and hydrogen peroxide should be noticed when running the chemical oxygen demand tests.