在溴化十六烷基三甲铵存在下2-溴-4,5-二羟基偶氮苯-4′-磺酸钠与铝反应的分光光度研究

Spectrophotometric study on reaction of aluminium(III) with sodium 2-bromo-4,5-dihydroxyazobenzene-4'-sulfonate in the presence of cetyltrimethylanunonium bromide

在阳离子表面活性剂存在下,2-溴-4,5-二羟基偶氮苯-4’-磺酸钠(BDAS)用于Fe(III)、Cu(II)、Mo(VI)、Ti(IV)、Pb(II)、W(VI)等金属离子的光度测定。BDAS与Al(III)形成二元络合物的反应已有人做过研究。本文研究了在阳离子表面活性剂溴化十六烷基三甲铵(CTMAB)存在下BDAS的离解平衡及BDAS与Al(III)的反应。三元络合物的形成提高了分析方法的灵敏度。表观摩尔吸光系数(ε=6.9×10~4)

Sodium 2-bromo-4, 5-dihydroxyazobenzene-4'-sulfonate (abbreviated as BDAS) Teacts with aluminium (III) in the presence of excessive cetyltrimethylammonium bromide(CTMAB) to form a water-soluble ternary complex. The complex has an absorption maximum at 527nm, maximum absoTbance was obtained in the pH range from 6.7 to 8.0. The absorbance of the complex was constant provided that the BDAS and CTMAB concentrations were higher than 1.4×10^(-4)M and 6.4×10^(-4)M, respectively. Absorbance of the reagent blank was effectively reduced by the addition of excessive sodium borate. Beer's law was obeyed over the range of 0～10μg of aluminium (III). The apparent molar absorptivity of the ternary complex is 6.9×10~4 l·cm^(-1)-mol^(-1) at 527 nm.The successive dissociation constants of the reagent were calculated on a PC-8001 computer according to A-pH curve. pK_1=6.56±0.20,pK^2= 11.42±0.15 if there is no CTMAB present in the solution. Otherwise pK_1=6.35±0.20, pK_2= 10.99+0.13. Addition of the surfactant strengthened dissociation of the reagent. The tolerance limits of some interfering ions were listed.