If you want to know the measuring principle of COD tester, you should first understand what COD is. COD is the abbreviation of Chemical Oxygen Demand, which is a method to measure organic pollutants in water. Organic substances in water samples are oxidized and decomposed by oxidants under certain conditions (usually high temperature, strong acid, excessive oxidant) to produce carbon dioxide and water. The chemical equivalent of oxidant required for oxidation is COD. Therefore, the detection value of COD is used to determine the content of organic substances in water samples. The higher the COD value is, the higher the content of organic matter in the water sample is, the more serious the water quality pollution is, and vice versa, the better the water quality is.
Determination principle of COD tester
COD tester is a common water quality measuring instrument. The measuring principle adopted is that we use a strong oxidant, such as high concentration potassium dichromate (K2Cr2O7), to oxidize with organic substances in water samples under high temperature and acidic conditions. The excessive amount of oxidant in this process ensures that the oxidant will react with all organic substances, and the unreacted oxidant can be measured by sensitive electrodes or optical sensors. Finally, the COD tester will use standardized built-in procedures to convert the concentration of residual oxidant into COD value. This conversion method is usually calculated according to the concentration of oxidant, the content of organic substances in the water sample and reaction conditions.
Common methods of COD tester
Ultraviolet (UV) absorption: measure the UV absorption value of the water sample after reaction, and calculate the concentration of residual oxidant according to the absorption value.
Silver mercury electrode method: immerse the electrode in the water sample after reaction, measure the potential change of the electrode, and calculate the concentration of residual oxidant according to the potential change.
Colorimetry: calculate the concentration of residual oxidant according to the degree of color change after water sample reaction.
The advantage of COD tester is that it can quickly and accurately measure the COD value in water samples, so it is widely used in water quality monitoring and quality control in the fields of environmental protection, industrial production and food processing. At the same time, COD tester can also measure and analyze at different levels according to different needs to meet the needs of different application fields.
