Discussion on the Method of Eliminating the Interference of Chloride Ions in the Determination of Chemical Oxygen Demand
As a comprehensive index to measure the relative content of organic pollutants in water,chemical oxy-gen demand(CODcr)is an important factor in water quality monitoring.The dichromate method is the most commonly-used method to determine CODcr,but its determination result is easily affected by the concentration of chloride ions in the water sample.This paper introduces four methods to eliminate chloride ion interference:the mercury sulfate shielding method,the chlorine correction method,the silver salt inhibition method and the standard curve correction method,and compares their respective application scopes and advantages and disadvantages,so as to help the monitoring personnel to choose the appropriate interference elimination method according to local con-ditions to improve the accuracy of analying test results.