异烟酸—巴比妥酸分光光度法测定水中氰化物的改进

Improvements of Methods to Determine Cyanide in Water with Isonicotinic-Barbituric Acid Spectrophotometry

采用《水质氰化物的测定容量法和分光光度法》(HJ 484—2009)中的方法 3(异烟酸—巴比妥酸分光光度法)测定水中氰化物时,在弱酸性条件下生成氯化氰,系统稳定性较差,需要快速操作,对实验技能要求高。基于原方法显色机理,提出了针对该方法的改进措施:提高氢氧化钠吸收液浓度;增加显色剂浓度,减少其加入体积;将加入磷酸盐缓冲溶液改为直接加入粉末状无水磷酸二氢钾,使得水中氰化物与氯胺T在中性条件下作用生成氯化氰,再进一步反应显色。改进后的方法稳定性好、检出限低、操作简便,对实际样品的测定结果令人满意。

During determination of cyanide in water by isonicotinic acid -barbituric acid spectro- photometric method in Water Quality--Determination of Cyanide ： Volumetric and Spectrophotometry Method （ HJ 484 - 2009）, cyanogen chloride was formed under weakly acidic condition, the system stability was poor, fast operation and high experimental skills were required. Based on the color developing mechanism of the former method, the improved method was put forward. By increasing the sodium hydroxide concentration and color developing agent concentration, reducing its addition volume, and adding directly powdered anhydrous potassium dihydrogen phosphate instead of the phosphate buffer solution, cyanogen chloride was formed with the interaction of chloramine-T and cyanide in water under neutral condition, and chromogenic reaction was conducted further. The improved method shows good stability, low detection limit, simple operation and has been applied to determine cyanide in actual samples with satisfactory results.