硅钼蓝分光光度法测定钒铝合金中硅

采用硝酸和盐酸分解样品,试液经煮沸除去氧氮化物后,用亚硫酸钠将五价钒还原为四价钒。微酸性溶液中,钼酸铵与正硅酸作用生成硅钼黄杂多酸,用硫酸亚铁铵将硅钼黄还原成硅钼蓝,建立了硅钼蓝分光光度法测定钒铝合金中硅的方法。结果表明,显色液中硅质量浓度在0.01～2.47 μg/mL范围内符合比尔定律,校准曲线的线性回归方程为y=4.433 x,相关系数R²=0.999 3。方法中硅的检出限和测定下限分别为0.003 3%和0.011%(质量分数)。实验方法应用于钒铝合金样品中硅的测定,测定结果的相对标准偏差(RSD,n=8)为0.17%～0.52%;加标回收率为99%～102%。按照实验方法测定钒铝合金样品中硅,结果与使用电感耦合等离子体原子发射光谱法的测定结果一致。

Determination of silicon in vanadium-aluminum alloy by silicon molybdenum blue spectrophotometry

The sample was decomposed by nitric acid and hydrochloric acid. After removing the nitrogen oxides by boiling, the pentavalent vanadium in sample solution was reduced to tetravalent vanadium. In weakly acid solution, the ammonium molybdate could react with silicic acid to form silicon molybdenum yellow heteropoly acid, which was then reduced to silicon molybdenum blue by ammonium ferrous sulfate. The determination method of silicon in vanadium aluminum alloy by silicon molybdenum blue spectrophotometry was established. The results showed that the Beer's law was obeyed for silicon when its mass concentration in coloring solution was in range of 0.01-2.47 μg/mL. The linear regression equation of calibration curve was y=4.433 x with correlation coefficient of R²=0.999 3. The detection limit and lower determination limit of silicon in this method was 0.003 3% and 0.011% (mass fraction), respectively. The proposed method was applied to the determination of silicon in vanadium aluminum alloy sample. The relative standard deviations (RSD, n=8) of found results were between 0.17% and 0.52%. The recoveries were between 99% and 102%. The content of silicon in vanadium aluminum alloy sample was determined according to the experimental method, and the found results were consistent with those obtained by inductively coupled plasma atomic emission spectrometry