基于NO_(2)的分离与富集光度法测定水中痕量NO_(2)^(-)

Spectrophotometric Determination of Trace NO_(2)^(-) in Water Based on the Separation and Enrichment of NO_(2)

在柠檬酸-乙醇介质中,NO^(-)_(2)被迅速转化成NO_(2),利用吹气分离法将其转移至净化空气中;净化空气中的NO_(2)与吸收液中的对氨基苯磺酸及N-(1-萘基)乙二胺盐酸盐发生显色反应进而被富集,由此水中痕量NO^(-)_(2)可采用分光光度法在540 nm波长处被间接测定。当采用三级吸收,以A=A_(1)+A_(2)+A_(3)作为响应值时,在拟定的实验条件下,NO^(-)_(2)的转化系数为83.5%,富集倍数为10倍,方法的线性范围在3.0~66.7μg/L之间。本方法有效消除了色度、浊度、盐分对NO^(-)_(2)测定的干扰,检出限为0.9μg/L,是国标法(GB 7493—87)的十分之一,可用于井水、河水中NO^(-)_(2)的测定,RSD<2.9%,回收率在96.6%~102.2%之间,表明该方法适用于测定水中痕量NO^(-)_(2)。

In citric acid-ethanol medium,NO^(-)_(2) was rapidly changed to NO_(2),which was transferred to purified air by air separation.The NO_(2) in purified air was enriched by undergoing color reaction with p-aminobenzene sulfonic acid and N-(1-naphthyl) ethylenediamine dihydrochloride in the absorption solution.Accordingly,the trace NO^(-)_(2) in water can be determined indirectly at 540 nm by spectrophotometric method.By using a three-stage absorption method with A=A_(1)+A_(2)+A_(3) as the response value,the obtained conversion coefficient of NO^(-)_(2) was 83.5% with the enrichment factor 10 and the linear range of determination 3.0~66.7 μg/L under the proposed experimental conditions.The interference of colority,turbidity and salinity to NO^(-)_(2) determination could be eliminated effectively with this method.The detection limit was 0.9 μg/L,which was a tenth of that of the national standard method(GB 7493—87).The relative standard deviation was less than 2.9% and the recovery was between 96.6%~102.2% when the method was applied to determine the trace NO^(-)_(2) in well water and river water,which indicated that the method was suitable for the determination of trace NO^(-)_(2) in water.