摘要:
在pH=4.5的HAc-NaAc缓冲溶液介质中,以溴化十六烷基吡啶(CPB)为增敏剂,痕量Cu(Ⅱ)能催化过氧化氢氧化溴酚蓝使之褪色,据此用于测定痕量铜。讨论了介质、试剂用量、反应温度、反应时间、表面活性剂及其共存离子的影响,确定测定波长为593 nm及最佳实验条件,测得反应表观活化能为90.3 kJ/mol。在优化条件下,方法检出限为0.646 ng/mL,Cu(Ⅱ)的质量浓度在0~0.064 μg/mL范围内与lg(A0/A)呈良好的线性关系,大多数常见元素不干扰测定。方法用于煤样中痕量铜的分析,5次测定的相对标准偏差小于3.1%,加标回收率在92.7%~107.0%,测定结果与原子吸收光谱法的结果一致。
Abstract:
A new catalytic kinetic spectrophotometry for the determination of copper has been established. The method is based on the catalytic effect of trace Cu (Ⅱ) on the oxidizing discoloring reaction of bromophenol blue with hydrogen peroxide using cetyl pyridinium bromide as a sensitizer in HAc-NaAc buffer solution at pH=4.5. Major factors such as acidity, reagent dosage, reaction temperature, reaction time, and the influence of surfactant and coexisting irons were studied. The detection wavelength was selected as 593 nm with optimal conditions. The apparent activation energy of the catalytic reaction was 90.3 kJ/mol. Under the optimal conditions, the detection limit of this method was 6.46×10-10 g/mL. In the content range of 0 to 0.064 μg/mL, there was a good linear relationship between the concentration of Cu(Ⅱ) and lg(A0/A). This method was simple, rapid, and highly selective. There were no interferences from the most common coexisting ions during determination. The proposed method was applied to the determination of trace copper in coal. The relative standard deviation was less than 3.1% (n=5), and the recoveries of standard addition were 92.7%-107.0%. The determination reults were consistent with those obtained by atomic absorption spectrometry.
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