过氧化氢氧化亚甲基蓝褪色催化动力学光度法测定镍

在pH 8.00的NH₃-NH₄Cl缓冲溶液中,在100 ℃加热条件下,痕量镍能催化过氧化氢氧化亚甲基蓝的褪色反应,建立了测定痕量镍的催化动力学光度方法。研究发现,非催化反应吸光度(A₀)和催化反应吸光度(A)在655 nm处的差值ΔA与镍的质量浓度在0.01～0.30 μg/mL范围内呈良好的线性关系,方法检出限为8.6×10^-3 μg/mL。该催化反应的表观速率常数为8.2×10^-4 s^-1,表观活化能为66.08 kJ/mol。方法用于延河水和自来水厂污水中痕量镍的测定,测定值与原子吸收光谱法一致,相对标准偏差(RSD,n=6)为1.2%～1.6%,加标回收率为99%~102%。

Catalytic kinetic spectrophotometric determination oftrace nickel based on fading reaction of methylene blue oxidized by hydrogen peroxide

The fading reaction of methylene blue oxidized by hydrogen peroxide could be catalyzed by trace nickel in NH₃-NH₄Cl buffer solution at pH 8.00 under heating condition at 100 ℃. Accordingly, a method was established for determination of trace nickel by catalytic kinetic spectrophotometry. It was found that the difference of absorbance (ΔA) between non-catalytic reaction (A₀) and catalytic reaction (A) at 655 nm had good linearity to the mass concentration of nickel in range of 0.01-0.30 μg/mL. The detection limit of method was 8.6×10^-3 μg/mL. The apparent rate constant of this catalytic reaction was 8.2×10^-4 s^-1, and the apparent activation energy was 66.08 kJ/mol. The proposed method was applied to the determination of trace nickel in waste water samples from Yanhe River and tap water plant. The results were consistent with those obtained by atomic absorption spectrometry. The relative standard deviation (RSD, n=6) was 1.2%-1.6%. The recoveries were between 99% and 102%.