強アルカリ溶液中でのアルセナゾIIIによるコバルト(II)の接触分析

概要

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A catalytic analysis based on a decomposition reaction of azo compounds is a highly sensitive determination method of Co(II). In the system which makes an azo compound to be an indicator reagent, metal complex formation with the azo compound is necessary for metal ions to be a catalyst. The arsenazo III used in this study as an indicator reagent is known to be a colorimetry reagent of rare earths. However, the formation of a complex with Co(II) was not known. It was found that Co (II) formed the complex in a strong alkaline medium and that it accelerated the color-fading reactions of arsenazo III. Then, a catalytic analysis method of Co (II) by arsenazo III in a strong alkaline medium was examined. A calibration curve was made between ln (A_1/A_<10>) and the concentration of cobalt(II), where A_1 and A_<10> were the absorbance of arsenazo III solution at 1 min and 10 min, respectively. The values of ln(A_1/A_<10>) were nearly proportional up to 20 ppb of cobalt (under the optimum conditions: pH 13.7, 1.9 × 10^<-5> M arsenazo III, 1.0% H_2O_2 and 45℃). The detection limit was 0.5 ppb. This method was applied to the determination of cobalt in silica gel without requiring any complicated pretreatment.
社団法人日本分析化学会の論文
2000-10-05