鉴于氰化物转化成氯化氰是HJ 484-2009中异烟酸-巴比妥酸分光光度法测定氰化物的独立中间环节,利用氯化氰沸点低(14 ℃)、稳定性好的特性,提出了基于吹气分离富集的异烟酸-巴比妥酸分光光度法测定水中痕量氰化物含量的方法。以空气为载气,以异烟酸质量浓度为17.20 g·L^-1、巴比妥酸质量浓度为8.40 g·L^-1的溶液为吸收液(pH 5.85),利用特定的分离富集装置,完成空气净化、氰化物转化成氯化氰、氯化氰分离、氯化氰吸收及转化成聚甲炔染料等一系列过程,采用分光光度计测定吸收液在600 nm处的吸光度。结果表明:当样品、吸收液的体积分别为60.0,5.00 mL,空气流量为0.10 L·min^-1,采用3级吸收,以总吸光度作为响应值时,氰化物转化系数为94.2%,富集倍数为11.3倍,检出限(3s/k)为0.1 μg·L^-1,测定线性范围为0.4~28.3 μg·L^-1;方法用于井水及河水中痕量氰化物的测定,氰化物质量浓度为1.2~8.9 μg·L^-1,回收率为92.9%~104%。

In view of the conversion of cyanide to cyanogen chloride is an independent intermediate step for the determination of cyanide by isonicotinic acid-barbituric acid spectrophotometry in HJ 484-2009, using the characteristics of low boiling point (14 ℃) and good stability of cyanogen chloride, a method for the determination of trace cyanide in water by isonicotinic acid-barbituric acid spectrophotometry based on air separation and enrichment was proposed. Using air as carrier gas and the solution with the mass concentration of isonicotinic acid of 17.20 g·L^-1 and barbituric acid of 8.40 g·L^-1 as absorption solution(pH 5.85), the specific separation and enrichment device was used for accomplishment a series of processes, including air purification, the conversion of cyanide to cyanogen chloride, the separation of cyanogen chloride, and the absorption of cyanogen chloride and conversion to polymethin dye, and the absorbance of absorption solution at 600 nm was measured by spectrophotometer. It was shown that the conversion coefficient of cyanide was 94.2%, and the enrichment factor was 11.3, with detection limit (3s/k) of 0.1 μg·L^-1 and linear range of determination was 0.4-28.3 μg·L^-1 when the volumes of the sample and absorption solution were 60.0 mL and 5.00 mL, respectively, and the flow rate of air was 0.10 L·min^-1 by using three-stage absorption and total absorbance as response value. The method was applied to determination of trace cyanide in well water and river water, in which the mass concentration of cyanide was in the range of 1.2-8.9 μg·L^-1, and the recoveries were in the range of 92.9%-104%.