甲基百里香酚蓝分光光度法测定铝合金中钛

准确、灵敏、快速地测定钛在铝合金材料中的含量,对提高铝合金材料的机械性能有重要意义。通过加入氢氧化钠溶液和双氧水溶解样品, Fe³⁺干扰可通过加入酒石酸钾钠溶液来消除, Zn²⁺干扰可通过加入二巯基丙磺酸钠溶液来掩蔽,Cu²⁺的干扰可通过加入铜试剂的方法来去除。使用稀H₂SO₄来控制体系的酸度,加入混合增敏剂阿拉伯树胶和聚乙烯醇,常温下甲基百里香酚蓝溶液会与钛发生显色反应形成稳定的蓝紫色络合物,利用该特性,实现了分光光度法对铝合金中钛的测定。实验结果表明:显色体系最大吸收峰为570 nm,钛质量浓度在小于1.6 μg/mL时与吸光度呈线性关系,线性相关系数r为0.999 4,方法检出限为2×10^-8(质量分数),表观摩尔吸光系数为4.7×10⁴ L·mol^-1·cm^-1。方法用于测定铝合金样品中钛的含量,结果的相对标准偏差(RSD,n=6)为2.1%~3.0%,加标回收率在97%～105%之间,测定值与采用GB/T 20975.12—2008的测定值基本一致。

Determination of titanium in aluminum alloy by methylthymol blue spectrophotometry

Accurate, sensitive and rapid determination of titanium content in aluminum alloy materials is of great significance for improving the mechanical properities of aluminum alloy materials. The sample was dissolved with sodium hydroxide solution and hydrogen peroxide. Potassium sodium tartrate solution, sodium dimercaptopropyl sulfonate solution and copper reagent were added respectively to eliminate the interference of Fe³⁺, Zn²⁺ and Cu²⁺. Dilute sulfuric acid was used to control the acidity of the system, and the mixed sensitizers composed of Arabic gum and polyvinyl alcohol were added. Methylthymol blue solution could react with titanium to form a stable blue-violet complex at room temperature. Based on this characteristic, the determination of titanium in aluminum alloy was realized by spectrophotometry. The experiment results showed that the maximum absorption peak of the chromogenic system was located at 570 nm. The mass concentration of titanium in the solution is linearly related to the absorbance within 1.6 μg/mL. The linear correlation coefficient (r) of calibration curve was 0.999 4. The limit of detection was 2×10^-8 (mass fraction). The apparent molar absorption coefficient was 4.7×10⁴ L·mol^-1·cm^-1. The proposed method was applied for determination of titanium in aluminum alloy samples. The relative standard deviations (RSD, n=6) of the determination results were between 2.1% and 3.0%. The recoveries were between 97% and 105%. The results were basically consistent with those obtained by GB/T 20975.12-2008.