在β-环糊精和阳离子表面活性剂作用下5-Br-TADEB分光光度法测定微量铑

Spectrophotometric determination of trace rhodium with 5-Br-TADEB in the presence of β-CD and cation surfactant CPB

研究了在 β-环糊精 ( β- CD)和各种不同类型表面活性剂存在下 5-溴 - ( 2 -噻唑偶氮 ) - 5-二乙氨基苯甲酸 ( 5- Br- TADEB)与铑的显色反应。在 p H 4.0～5.7的 HAc- Na Ac介质中 ,Rh3 +与 5- Br- TADEB形成稳定的 1∶ 2蓝色络合物 ,最大吸收波长位于 687nm处。阴离子和非离子表面活性剂对体系无明显作用 ,β- CD和阳离子表面活性剂分别加入使体系灵敏度提高 2 0 % ,而当 β- CD与阳离子表面活性剂同时加入则可使体系灵敏度提高 50 % ,其表观摩尔吸光系数ε=1 .1 4× 1 0 5L·mol-1·cm-1。

The colour reaction of 5 bromo (2 thiazolylazo) 5 diethylaminobenzoic acid(5 Br TADEB)with rhodium(Ⅲ) was studied systematically. The effects of β CD and surfactant on the colour reaction was investigated. Based on this, a new photometric method for determination of micro amounts of Rh(Ⅲ) was developed. In a HAc NaAc buffer solution of pH 4.75 and in the presence of β CD and cationic surfactant CPB, rhodium(Ⅲ) reacts with 5 Br TADEB to form a 1∶2 stable blue complex,exhibiting an absorption maximum at 687nm. The molar absorptivity is 1.14×10 5 L·mol -1 ·cm -1 and Beer′s law is obeyed in the range of 0～0.6μg·mL -1 Rh. The method was applied to the determination of of rhodium(Ⅲ) in catalysts with satisfactory results.