多直线分光光度法快速测定化学需氧量

Quick evaluation of chemical oxygen demand based on spectrophotometric and multi-linear analysis

采用标准的微量密闭消解-分光光度法测定了邻苯二甲酸氢钾水溶液的化学需氧量（COD），该标准所规定的从低浓度到高浓度拟合一条直线方程来计算待测水样的COD值的方法误差较大，难以满足检测精度的要求，因此提出了测定溶液COD值的多直线分光光度法，即在低浓度（20-100 mg/L）和高浓度（100-700 mg/L）范围分别拟合一条直线，并采用快速密闭消解的方法。结果表明，该方法的精确度比标准方法的高，尤其是在低浓度范围，且消解速度可从标准规定的2 h减少到45 min。

The chemical oxygen demand （COD） of solutions of potassium hydrogen phthalate were determined by using the standard technique of a miniaturized closed decomposition system with spectrophotometric analysis. It was found that the relationship between concentration and COD showed a relatively large deviation from linearity. A new method of spectrophotometric determination of COD, incorporating multi-linear analysis is described, which uses two different linear relationships derived from measurements at low concentration （20 - 100 mg/L） and high concentration （100- 700 mg/L）. The results showed that the new method is more accurate than the standard linear analysis, especially in the low concentration range （20- 100 mg/L）, and furthermore that the time required for the decomposition can be reduced from 2 h to 45 min.