Liu D
Department of Chemistry, Hebei Normal University, 050091 Shijiazhuang.
Guang Pu Xue Yu Guang Pu Fen Xi. 2000 Dec;20(6):883-5.
In this paper, ways of determining the composition and formation constants for rare earths (La3+, Pr3+)-DBS-Arsenazo (2-(2-arsonophenylazo)-7-(2,6-dibromo-4-sulphophenylazo)-1,8-dihydroxy-3, 6-naphthalene-disulfonic acid) complexes were discussed. La3+ or Pr3+ (colorless) reacts with DBS-Arsenazo which absorbs at 535 nm, blue-violet products absorbing at 630 nm are formed in 1 mol.L-1 HCl solution. To study the reactions, a series of spectra of the complexes were obtained by spectrophotometric titration of DBS-Arsenazo with La3+ or Pr3+. The number of the components contributing to the color systems was obtained by using factor analysis method. It shows that only two color components are in the system. Combined with structural consideration, it is possible that the reactions is as follows: La3+ or Pr3+ + nDBS-Arsenazo = La3+ or Pr(3+)-(DBS-Arsenazo)n Coloress absorbs at 535 nm absorbs strongly at 630 nm A linear regression method was proposed to determine the compositions, the formation constants and the concentration of the color reagent. The results show that La3+ or Pr3+ reacts with DBS-Arsenazo, and form 1:3 complexes in 1 mol.L-1 HCl solution. The conditional formation constants (log beta 3) determined are 15.36 and 15.34 respectively.
本文讨论了测定稀土（La3+、Pr3+）-二溴磺酸偶氮胂（2-（2-胂酸基苯偶氮）-7-（2,6-二溴-4-磺酸基苯偶氮）-1,8-二羟基-3,6-萘二磺酸）配合物的组成和形成常数的方法。La3+或Pr3+（无色）与在535nm处有吸收的二溴磺酸偶氮胂反应，在1mol·L-1 HCl溶液中形成在630nm处有吸收的蓝紫色产物。为了研究这些反应，通过用La3+或Pr3+对二溴磺酸偶氮胂进行分光光度滴定，获得了一系列配合物的光谱。采用因子分析法得到了对颜色体系有贡献的组分数量。结果表明该体系中只有两种颜色组分。结合结构考虑，反应可能如下：La3+或Pr3+ + n二溴磺酸偶氮胂 = La3+或Pr(3+)-(二溴磺酸偶氮胂)n 无色 在535nm处有吸收 在630nm处有强吸收 提出了一种线性回归方法来测定配合物的组成、形成常数和显色剂的浓度。结果表明，La3+或Pr3+与二溴磺酸偶氮胂反应，在1mol·L-1 HCl溶液中形成1:3的配合物。测定的条件形成常数（logβ3）分别为15.36和15.34。
