COD pre loaded reagent

COD pre loaded reagent

COD pre loaded reagentUsing the dichromate method, it is used for the determination of chemical oxygen demand in various types of water bodies such as environmental water, seawater, agricultural irrigation water, municipal sewage, and industrial wastewater. The chloride ions in the water sample are the main interfering components. When the chloride ion concentration is below 2000mg/L, this pre prepared reagent can be used directly, otherwise dilution and other methods need to be used for treatment. For high chlorine containing reagents, a chlorine resistance capacity of 20000mg/L has been designed.

1. This method refers to the standard method of the Ministry of Environment "HJ/T 399-2007 Determination of Chemical Oxygen Demand in Water Quality - Rapid Digestion Spectrometric Method". The sample is heated together with sulfuric acid and strong oxidant potassium dichromate at 165 ℃ for 20 minutes. Reductive organic compounds participate in the reaction, reducing dichromate ions to green trivalent chromium ions.

When the COD value in the sample is 20-1500mg/L or 200-15000mg/L, measure the absorbance of trivalent chromium produced by the reduction of potassium dichromate at a wavelength of 620nm. The COD value in the sample is directly proportional to the increase in absorbance of trivalent chromium, and convert the absorbance of trivalent chromium to the COD value of the sample.

3. When the COD value in the sample is 3-150mg/L, measure the total absorbance of the two chromium ions, hexavalent chromium that has not been reduced by potassium dichromate and trivalent chromium that has been reduced, at a wavelength of 420nm; When the COD value in the sample is 0.7-40mg/L, measure the total absorbance of two chromium ions, hexavalent chromium and trivalent chromium, at 350nm. The COD value in the sample is directly proportional to the decrease in absorbance of hexavalent chromium, the increase in absorbance of trivalent chromium, and the decrease in total absorbance. Convert the total absorbance value to the COD value of the sample.

4. The reagent also contains silver and mercury salts. The function of silver salt is to act as a catalyst, while the function of mercury salt is to chelate chloride ions to shield them from interference.