连续流动分析法测定水中总氰化物的研究

Determination of total cyanide in water by continuous flow analysis

建立了连续流动分析仪测定水中总氰化物的方法,方法的标准曲线相关系数r^2为1.0000,方法检出限为0.169μg/L,不同浓度样品测定的相对标准偏差为0.6%～1.2%,加标回收率为94.3%～101.2%,该方法具有良好的精密度、较高的准确性。探讨了蒸馏温度、试剂pH值、亚硝酸钠和硫化钠两种干扰物以及水样保存条件对水中总氰化物测定的影响。以本方法标准曲线对氰化钠、铁氰化钾、六氰基钴酸钾进行测定,分析了不同结构的氰化物对回收率的影响。实验结果表明,测定水中总氰化物的最佳蒸馏温度为120℃,当缓冲溶液pH值≤2.7时,蒸馏试剂pH值≤1.2时,显色剂pH值≤2.8时,影响实验反应进行,测试结果偏低。当样品中亚硝酸钠干扰物的浓度小于1.5mg/L,硫化钠的浓度小于100mg/L时,对样品总氰化物的测定结果影响较小。利用总氰化物标准曲线,测定5～100μg/L的氰化钠和铁氰化钾标准溶液的回收率分别为100.7%～104.2%和94.8%～111.8%;六氰基钴酸钾溶液的回收率较低,为13.4%～20.4%,与《水质氰化物的测定流动注射-分光光度法》(HJ 823-2017)测试范围一致。当加入氢氧化钠调节水样pH≥12,水样在4℃冷藏保存16天时,其加标回收率在97%以上。

In this paper,the distillation temperature,the pH of reagents,the interferences including sodium nitrite and sodium sulfide,and the preservation conditions of samples for the determination of total cyanide in water were discussed.The experimental results showed that the optimum distillation temperature was 120℃.When the pH value of the buffer solution was below 2.7,the pH value of the distillation reagent was below 1.2 and the pH value of color reagent was below 2.8,the reaction was affected and the results were lower.When the concentrations of the sodium nitrate in the samples were lower than 1.5 mg/L and the concentrations of sodium sulfide were lower than 100 mg/L,the effects were not significant.The recoveries of sodium cyanide and potassium ferricyanide with the concentration of 5-100μg/L were within 100.7%-104.2%and 94.8%-111.8%,respectively,the recoveries of potassium hexacyanocobaltate was in the range of 13.4%-20.4%.The results were consistent with the testing range of Water quality-Determination of cyanide-Flow injection analysis and spectrophotometry method(HJ 823-2017).When the pH value of water samples was larger than 12 by adding sodium hydroxide and the water samples were stored at 4℃for 16 days,the recoveries of the water samples were above 97%.