在十二烷基硫酸钠存在下用3,5-二Br-PADAP分光光度法测定微量银

SPECTROPHOTOMETRIC DETERMINATION OF MICROGRAMME LEVEL OF SILVER WITH 3,5-DIBROMOPADAP IN THE PRESENCE OF SDS

研究了在阴离子表面活性剂十二烷基硫酸钠(SDS)存在下,2(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚(3,5-二Br-PADAP)与银的显色反应。实验结果表明,显色的适宜酸度为pH3-8,络合物的最大吸收波长为570nm,在此波长下测得其表观摩尔系数为7.7×10~4,银量在0-25μg/25ml范围内遵守比尔定律。络合物组成比为Ag:R=1:2,本法以EDTA作掩蔽剂可以不经分离,直接测定简单样品中的银。

The colour reaction of silver with 2 [(3,5-dibromo-2-pyridyl) azo]-5-diethylaminophenol (3,5-dibromo-PADAP) in the presence of sodium dedecylsulfate (SDS) has been studied. A stable complex of silver with 3, 5-dibromo-PADAP is formed in the medium of pH 3- 8. Its molar absorptivity is 7.7×10~4 at maximum absorbance of 570nm. Beer's law is obeyed within 0-25μg silver per 25ml. The composition ratio of silver to 3,5-dibromo-PADAP is 1:2. The interference of some elements can be effectively eliminated by adding EDTA (0.1 mol/L). The method has been applied to the direct determination of silver in ores.