空白值校正法无汞快速测定地表水化学需氧量

探讨了K2Cr2O7在不同酸度的硫酸介质中的化学行为,确定9 mol/L H2SO4为K2Cr2O7法测定地表水COD的合理酸度。多种有机物消解试验及半年多地表水样跟踪检测,将消解回流时间从2小时缩短到30分钟之内是可行的。氯离子(Cl-)干扰可用生成AgCl沉淀和空白值校正的办法消除。此方法的检出下限是11mg/L,样品测定的加标回收率在96%～101%。此方法不仅缩短了回流时间、减少了汞带来的二次污染,从而实现无汞快速测定地表水COD。

Determination of COD in Surface Water with Non-Mercury by Blank Correction

This article explores the K2Cr2O7 chemical behavior in different acidity of the sulfuric acid medium,and determines the reasonable acidity of surface water for COD testing and the concentration of H2SO4 is 9 mol/L.A variety of organic matter digestion trials and more than six months of surface water sample tracking and detection prove that digestion reflux time reduced from two hours to 30 minutes is feasible.The interference of chloride ion（Cl-） can be eliminated by generating AgCl precipitation and the blank value correction method.The detection of this method is 11 mg/L,determination of recovery rate is from 96%~110%.It not only shortens reflux time but also reduces secondary pollution from mercury,it achieves determination of surface water without mercury rapidly.