ジベンゾ-18-クラウン-6及び4-[[4-(フェニルアミノ)フェニル]アゾ]-2,5-ジクロロベンゼンスルホン酸を用いる河川水中のカリウムの抽出-吸光光度定量

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An extraction-spectrophotometric method for the determination of potassium by means of a new reagent, 4-[[4-(phenylamino)phenyl)azo]-2, 5-dichlorobenzene-sulfonic acid (TOOCl_2) was proposed. The complexes of potassium ions with dibenzo-18-crown-6 (DB18C6) associate with TOOCl_2 anions to give colored ion pairs which can be extracted into benzene. The ion pairs in benzene exhibit a maximum absorption at 430 nm with an apparent molar absorption coefficient of 9300 dm^3 mol^<-1> cm^<-1>. Potassium in river water was determined as follows : To a 50-cm^3 vessel with a stopper, 5 cm3 of an aqueous TOOCl_2 solution (0.02 mol dm^<-3>), 5 cm^3 of an aqueous Li_2 (EDTA) (0.001 mol dm^<-3>) solution, and 10 cm^3 of a water sample were transferred. The resulted solution was shaken with 20 cm^3 of a benzene solution of DB18C6 (0.01 mol dm^<-3>) for 30 min at 20℃. After the mixture was allowed to stand for 30 min, the absorbance of the benzene phase was measured at 430 nm against a reagent blank. Interferences from calcium (II) and magnesium (II) were avoided by complexing with EDTA. Sodium ions up to 8 ppm gave virtually no interference. Potassium concentrations determined by means of the proposed method agreed closely with those of atomic absorption spectrophotometry.
社団法人日本分析化学会の論文
1985-09-05