クロラニル酸バリウムを用いる硫酸イオンの高感度吸光光度定量

概要

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Chrome Azurol S (CAS) was found to be effective for increasing the sensitivity of the barium chloranilate method for sulfate ion. On the treatment of sulfate ion {(5〜25) μg} with barium chloranilate (40 mg) in 80% 2-propanol aqueous medium (17 ml), free chloranilate anion was released stoichiometrically by the sulfate. The precipitate of barium sulfate was filtered off. The chloranilate in a portion (15ml) of the filtrate was then separated from the 2-propanol on a column (10cm, diam. 5 mm) of activated alumina (0.16 g), by washing the column with water and eluting the chloranilate with 4 ml of 0.1 M aqueous ammonia. The chloranilate anion in the eluate was extracted with tris(1,10-phenanthroline)iron(II), Fe(phen)_3^<2+>, at pH 2 into nitrobenzene (5 ml) as an ion-pair complex. After removal of the aqueous layer the nitrobenzene layer was shaken again with 12.5ml of an aqueous solution (pH 5) containing CAS (10^<-5> M) for 3 min. The chloranilate in the complex was quantitatively replaced by CAS, thus forming CAS-Fe(phen)_3 complex in the nitrobenzene. The absorbance of the CAS complex was measured at 600 nm with 1-cm cells against a reagent blank. The ε value of the present method was 2.3 × 10^4 l mol^<-1> cm^<-1>. For a rain sample containing 2.20 ppm of sulfur oxides the coefficient of variation of 6.60% was obtained in six replicate determinations.
社団法人日本分析化学会の論文
1979-10-05