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迄今为止,直接于水相中光度法测定Ag~+的有机试剂为数不多.一般采用二硫腙,二甲氨基苄叉罗丹宁或DDTC等萃取比色方法.这类萃取比色方法需用大量的有机溶剂,而很多有机溶剂的毒性较大.我们曾合成了多只8-羟基喹啉-5-磺酸的偶氮类试剂,发现其中的7-(4-氯-2-硝基苯偶氮)-8-羟基喹啉-5-磺酸(CNAQS)可作为Ag~+的水相分光光度测定的显色剂.显色反应的最适酸度为pH 4～4.5;络合物的最大吸收波长在570nm处;摩尔吸光系数为3.27X10~4:Ag~+与CNAQS的络合比为1∶2;测得络合物的表观稳定常数为1.26X10~(10).使用本试剂测定阳极泥中的微量银,所得结果与原子吸收光度相比较非常一致. Tavaras,T.等曾建议使用该试剂于Cd~(2+),Cu~(2+),Ni~(2+),Zn~(2+)和Mo(Ⅵ)等离子的光度法测定,但用作银离子的显色剂,未见报道.
So far, there are only few organic reagents for the determination of Ag ~ + directly in the aqueous phase, generally using the extraction colorimetric method such as dithizone, dimethylazide and rhodanine or DDTC etc. Such extraction and colorimetric methods require A large number of organic solvents, and many organic solvents more toxic we have synthesized more than 8-hydroxyquinoline-5-sulfonic acid azo reagent and found that 7- (4-chloro-2-nitro Phenylazo) -8-hydroxyquinoline-5-sulfonic acid (CNAQS) can be used as a color reagent for the aqueous phase spectrophotometry of Ag ~ +.The optimal acidity of the color reaction is pH 4-4.5; The maximum absorption wavelength was at 570nm, the molar absorptivity was 3.27X10 ~ 4, the complex ratio of Ag ~ + to CNAQS was 1: 2, and the apparent stability constant of the complex was 1.26X10 ~ (10) This reagent was used to determine trace silver in anode slime and the results were very consistent with the atomic absorption spectrophotometry. Tavaras, T. et al. Proposed the use of this reagent in Cd ~ (2 +), Cu ~ (2 +), Ni ~ (2) +), Zn ~ (2+) and Mo (Ⅵ), but it has not been reported as a chromogenic reagent for silver ion.