光度滴定法判断COD的滴定终点

of the Titration Endpoint of COD

提出了判断化学需氧量(COD)滴定终点的新方法——光度滴定法,分析比较了光度滴定法和现有国标法的区别。试验结果表明:滴定终点红褐色溶液最佳吸收可见光波长是510 nm;滴定反应速度不影响光度滴定终点的确定;光度滴定曲线能够较好地确定滴定终点;实际水样测定中,国标法和光度滴定法的滴定终点判断误差分别为1.12%和0.84%;光度滴定法的相对标准偏差小于1.20%,与国标法相比无显著性差异。光度滴定法以光学的角度判断COD的滴定终点,避免了国标法的视觉判断误差,为未来检测仪器的全自动化提供了新思路。

A new method called as spectrophotometric titration was proposed to determine the titration endpoint of chemical oxygen demand(COD).The differences between the methods of spectrophotometri titration and national standard were analyzed.The experimental results show that the visible wavelength which can be optimally absorbed by the red-brown solution at the titration endpoint is 510 nm.The reaction rate of titration does not affect the determination of the spectrophotometric titration endpoint.The spectrophotometric titration curve can finely determine the titration endpoint.The determination errors of the titration endpoint by the two methods applied in practical samples are 1.12%and 0.84%respectively.The relative standard deviation of the spectrophotometric titration method is less than 1.20%,which is of no significant difference compared to the national standard method.The spectrophotometric titration method can determine the titration endpoint from an optical angle.It avoids the visual error by the national standard method,and provides new ideas for developing the full automation of detection instruments in the future.