季铵盐杀菌剂对硬度测定的干扰与消除

Interference of Quaternary Ammonium Biocide in Hardness Determination and Its Elimination

采用EDTA滴定法测定循环水硬度时,季铵盐杀菌剂会对滴定产生干扰,导致无法观察滴定终点,为此分析了产生干扰的原因,并通过试验研究了消除干扰的三种方法。结果表明,四苯硼钠沉淀法、过硫酸铵氧化分解法和二甲酚橙指示剂法均可消除季铵盐杀菌剂对硬度测定的干扰,得到满意的测定结果。相比之下,四苯硼钠沉淀法操作简单、测定结果准确,更适合循环水硬度的现场监测。

When EDTA titration method is used to determine the hardness of recirculated cooling water, quaternary ammonium biocides may produce interference in titration and cause the end point of titration to be invisible. Therefore, the reasons of the phenomenon were investigated, and three solutions were developed. The experiment results show that the three methods, including sodium tetraphenylboron precipitation method, ammonium persulfate oxidation method and xylenol orange indicator method, are all able to eliminate the interference of quaternary ammonium biocides in the determination of hardness, and satisfactory determination results can be obtained. By comparison, the sodium tetraphenylboron precipitation method is more suitable for in-situ monitoring the hardness of recirculated cooling water for its simple operation and accurate result.