过氧化氢氧化亚甲基蓝褪色催化光度法测定铝合金中痕量镍

基于在pH 5.6的Na₃C₆H₅O₇-NaOH缓冲溶液中,痕量镍对H₂O₂氧化亚甲基蓝(MB)的褪色反应具有催化作用且褪色的程度与镍的含量成线性关系,建立了催化动力学光度法测定痕量镍的新方法。研究了影响催化褪色反应的因素,并测定了一些动力学参数。结果表明,非催化反应体系与催化反应体系的最大吸收波长均在664 nm处,方法的线性范围为0.02～1.4 μg/mL,线性回归方程为lg(A₀/A_t)=0.776 5 ρ(μg/mL)+0.157 1,相关系数r =0.998 6,检出限为0.011 8 μg/mL,反应的表观活化能为25.14 kJ/moL。方法用于铝合金标准样品中痕量镍的测定,结果与认定值基本一致,相对标准偏差(RSD)为2.9%和2.8%(n=5),回收率在98%～104%范围。

Catalytic spectrophotometric determination of trace nickel in aluminum alloy based on the discoloring reaction of methylene blue by oxidation of hydrogen peroxide

In Na₃C₆H₅O₇-NaOH buffer solution at pH 5.6, trace nickel had catalytic effect on the fading reaction of methylene blue (MB) oxidized by hydrogen peroxide and the fading degree was linear to the content of nickel. On the basis of these, a new method for catalytic-kinetic spectrophotometric determination of trace nickel was established. The influence factors on the catalytic fading reaction were studied and some kinetic parameters were determined. The results showed that the non-catalytic reaction system and the catalytic reaction system had the same maximum absorption wavelength at 664 nm, and the linear range was 0.02-1.4 μg/mL. The regression equation was lg(A₀/A_t)=0.776 5ρ(μg/mL)+0.157 1 with correlation coefficient r=0.998 6 and detection limit of 0.011 8 μg/mL. The apparent activation energy was 25.14 kJ/mol. The method had been applied to determine trace nickel in aluminum alloy samples, and the results were basically consistent with the certified values. The relative standard deviation (RSD, n=5) was 2.9% and 2.8%, and the recoveries was 98%-104%.