论文部分内容阅读
5-溴-PADAP是目前测定多种金属元素的高灵敏显色剂。据文献[1]报道,在弱酸性介质(pH 4.8)中,该试剂与锆(Ⅳ)可以形成一蓝紫色络合物,其最大吸收峰位于583nm,摩尔吸光系数为1.35×10~5(ι·mol~(-1)·cm~(-1))。虽然此显色体系具有较高的灵敏度,但是,由于显色酸度过低,方法不可能获得满意的选择性和稳定性。我们发现,在阴离子表面活性剂胶束的存在下,上述显色反应的吸光性质和反应条件都发生了明显的变化。当酸度条件基本维持不变时,即在pH=3.0～5.0的介质中,络合物的吸收峰由583nm移至634nm,摩尔吸光率则激增至3.15×10~5(ι·mol~(-1)·cm~(-1))。当显色酸度移至0.1～0.3N HNO_3介质中时,二元络合物的摩尔吸光率下降至2.9×10~4(ι·mol~(-1)·cm~(-1)),而胶束络合物的吸收峰却移至645nm,摩尔吸光率仍可达到1.15×10~5(ι·mol~(-1)·cm~(-1))。显然,在此条件下,显色体系的选择性和稳定性都得到了保证。
5-bromo-PADAP is a highly sensitive reagent for the determination of various metal elements. It has been reported in the literature [1] that this reagent forms a blue-violet complex with zirconium (Ⅳ) in a weakly acidic medium (pH 4.8) with a maximum absorption peak at 583 nm and a molar extinction coefficient of 1.35 × 10 -5 ( ι · mol -1 (cm -1)). Although this color system has high sensitivity, it is impossible to obtain satisfactory selectivity and stability due to the low acidity of the color system. We found that in the presence of anionic surfactant micelles, the absorbance properties of the above color reaction and the reaction conditions have undergone significant changes. When the condition of acidity is almost the same, the absorption peak of complex increases from 583nm to 634nm and the molar absorptivity increases sharply to 3.15 × 10 ~ 5 (ι · mol ~ (- 1) · cm -1). The molar absorptivity of the binary complex decreased to 2.9 × 10 ~ 4 (ι · mol -1 cm -1) when the chromogenic acidity was shifted to 0.1-0.3 N HNO 3. The absorption peak of micellar complex shifted to 645 nm, and the molar absorptivity could still reach 1.15 × 10 ~ 5 (ι · mol -1 cm -1). Obviously, in this condition, the color system selectivity and stability are guaranteed.