水体暂时硬度测定的EDTA滴定法

Determination of Temporary Hardness in Water by EDTA Titration

目的研究EDTA滴定法测定水体暂时硬度的检测方法。方法配制一系列待测溶液,研究碳酸氢钙在加热条件下完全分解产生碳酸盐沉淀所需要的最适时间,分析该方法的检出限,并用加标回收方法分析方法的回收率和精密度。结果加热30 min时,不同浓度下碳酸盐均可完全沉淀。方法的最低检出限为14 mg/L,小于等于此浓度时,实验误差较大。该方法的加标回收率在95.92%～179.14%之间,其中浓度为14.66 mg/L时由于误差较大,所以加标回收率偏差最大为179.14%。当样品浓度高于50 mg/L时,方法相对标准偏差(RSD%)为4.2%～4.4%。结论该检测方法操作和计算简便,精密度较高。

[Objective]To study the determination of temporary hardness in water by EDTA titration.[Methods]A series of solution to be measured was prepared to research the proper time for Ca（HCO_3）_2 decompounding into CaCO_3 completely when heated.The detection limit was analyzed.The recoveries and precision of this method were also discussed by standard recovery method.[Results]After heating for 30 min,Ca（HCO_3）_2 could all decompound into carbonate completely under different concentration.The minimal detect limit was 14 mg/L under which the experimental error is larger.The recoveries of this method are between 95.92%～179.14%.The relative standard deviation（RSD%） was 4.2%～4.4% when the solutions are thicker than 50 mg/L.[Conclusion]Operation and calculation of this monitoring method are easy and the results are more precise.