过氧化氢在铬的原子吸收光谱测定法中的应用

THE ROLE OF HYDROGEN PEROXIDE IN ATOMIC ABSORPTION SPECTROSCOPIC DETERMINATION OF CHROMIUM

本文作者在参加研究铬(Ⅵ)和铬(Ⅲ)的二乙胺硫代甲酸钠/甲基异丁基甲酮(以下简作DDTC/MIBK)络合萃取-火焰原子吸收光谱测定法并用于样品分析时,曾发现影响精密度的关键步骤是氧化。经严格控制酸度、体积与加热条件后已获解决。但是,当某些样品需要破坏有机物而加酸消煮、蒸干时,再度出现精密度难以保证,测得值系统偏低的现象;然而在萃取分层后的水相中却并未发现有遗留的铬。

When perchloric or sulfuric acid is used to destroy the organic matters in the testing sample and to oxidize chromium(Ⅲ) for the determination of total chromium content of waste water and slags, some chromium might be lost owing to the formation of volatile chromyl chloride. This drawback can be avoided if hydrogen peroxide in an alkaline medium is used as oxidizing agent. In this paper, the testing procedures of the proposed method are described and the oxidation-reduction behavior of hydrogen peroxide during the sodium diethyldithiocarbamate-methyl isobutyl ketone(DDTC—MIBK) chelate extraction process of chromium(Ⅵ) is discussed. The suggested method has been used on soil samples containing 3—100ppm of total chromium. The relative standard deviation(n=8) is 3.4%.