Rapid Determination of CODMn in Water Sample by Spectrophotometry

For determination of CODMn of water sample, 100.0 mL each of water sample and blank water sample were taken and placed in conical flasks separately. After acidifying with H2SO4 solution, 18.00 mL of 2.0×10-3mol·L-1 KMnO4 solution were added to each of the flasks and the solutions were heated in a water bath for 10 min. After cooling and centrifuging, absorbances A0 and A of the supernatants were measured at 520 nm with 1 cm absorption cell vs. H2O as reference. Difference of absorbances ΔA(A0-A) represents the amount of KMnO4 consumed by its reaction with the reducing substances present in water sample. Value of CODMn of the sample was found from the calibration curve prepared by standard solution of CODMn.