Determination of COD by spectrophotometry with self-prepared digestion solution

Key words: 
• COD measurement /
• dichromate method /
• colorimetry /
• substitute agent

Abstract: Determination of COD by spectrophotometry is performed by replacing the high-cost special digestion reagent of ThermoFisher’s AQ4001COD system with the selfprepared digestion solution in the present study. The results showed that COD determination by spectrophotometry with selfprepared digestion solution exhibits a higher precision and accuracy. Furthermore, no significant differences for COD determination value are found between China national standard method (GB 119141989) and the abovementioned spectrophotometry with selfprepared digestion solution . The standard deviation of COD determination values by spectrophotometry with selfprepared digestion solution varies from 1.38% to 2.53% for water sample with a lower COD concentration from 30 to 150 mg/L ,from 0.47% to 3.63% for water sample with a middle COD concentration ranged from 0 to 1 500 mg/L, and from 017% to 3.53% for water sample with a higher COD concentration of more than 3 000 mg/L. It is concluded that COD determination by spectrophotometry with selfprepared digestion solution is suitable to determine COD values for all kinds of water samples instead of tannery wastewater. The method of spectrophotometry has the advantages of small quantity of reagent, speed measurement, economization and low pollution,and should be applied popularly in the field of environmental science and wastewater analysis.