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近年来,有关催化动力学光度法测定铜的报道渐多,但此类方法一般要求条件严格,目前尚无共同认可的方法。文献[5]报道,ClO_3~-对I~-的氧化反应速度缓慢,但在一定酸度下,Mo(Ⅵ)可催化该反应。我们研究用ClO_3~--Mo(Ⅶ)-I~--淀粉氧化还原反应系测定氯酸盐时发现,在1.6mol·L~(-1)H_2SO_4介质中反应进行得很快;但pH>2时,反应明显变慢。进一步的研究发现,在弱酸性体系中,Cu(Ⅱ)对该反应系具有显著的二次催化作用;而且在一定条件下,二次催化及一次催化反应体系在585nm波长处的吸光度之差与一定范围内的Cu(Ⅱ)浓度成正比。在此基础上提出了一种测定微克级铜的动力学新方法,线性范围为Cu(Ⅱ)0～9.8μ·ml~(-1).
In recent years, more and more reports on the determination of copper by catalytic kinetic spectrophotometry have been reported. However, such methods generally require strict conditions and there is no commonly accepted method. It has been reported in literature [5] that the oxidation reaction of ClO_3 ~ - on I ~ - is slow, but Mo (Ⅵ) catalyzes the reaction at a certain acidity. We found that chlorate was detected by ClO_3 ~ --Mo (Ⅶ) -I ~ -starch redox reaction, and the reaction proceeded rapidly in 1.6mol·L -1 H_2SO_4 medium; however, pH> 2, the response was significantly slower. Further study found that Cu (Ⅱ) has a significant secondary catalytic effect on the reaction system in weak acid system. And under certain conditions, the difference between the absorbance at 585 nm of the secondary and primary catalytic systems is similar to A certain range of Cu (Ⅱ) concentration is proportional to. On this basis, a new kinetic method for the determination of microgram copper was proposed. The linear range was 0 ~ 9.8μ · ml -1 Cu (Ⅱ).