潜媒抽出-原子吸光分析法によるクロム(III)とクロム(VI)の分別定量

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Masking a large amount of Cr(III) with EDTA, micro amounts of Cr(VI) were extracted into mentyl isobutyl ketone (MIBK) as diethyl dithiocarbamate (DDTC) complex and analyzed by atomic absorption spectrophotometry. (a) Determination of Cr(VI): Take a sample solution {containing less than 50μg of Cr(VI)} into a 100ml beaker, and 10.0ml of 0.2M EDTA solution and boil for 5 min. After cooling to room temperature, adjust the pH value to 4〜5. Transfer the solution to a 100ml separatory funnel, add 2.5ml of 2% DDTC solution and make the total bolume of it to 50ml with distilled water. Add 10.0ml of MIBK and shake the solution vigorously for 5 min. Wash the stopper of the separatory funnel with samll quantities of water and stand for 10min. Separate the layers and measure the Cr concentration in the MIBK extract with a Hitachi model 207 atomic absorption spectrophtometer, using air-acetylene flame (analytical line;3579Å). The extractability of Cr(VI) was 74.8%. The respective presence of less than 5-fold Bi(III), 20-fold Co(II), 10-fold Fe(III) and 5-fold V(V) of Cr(VI) did not interfere. (b) Determination of total Cr: Take a sample solution (containing less than 20μg of Cr) into a beaker, add 2ml of (1+4) H_2SO_4. Add 0.01N KMnO_4 solution dropwise while heating until the solution becomes faintly pink, and boil for 5 min. After cooling, dilute to constant volume with distilled water. Then, take a given bolume(containing less than 40μg of Cr) of the solution, adjust the pH value to 4〜5. Transfer the solution to a 100ml separatory funnel and determine amounts of Cr as the procedure (a) after addition of 2% DDTC solution. The extractability of Cr(VI) in this case was 98.1%. Amounts of Cr(III) were calculated from differernce between those of total Cr and Cr(VI). The relative error was +3%.
社団法人日本分析化学会の論文
1975-11-10

潜媒抽出-原子吸光分析法によるクロム(III)とクロム(VI)の分別定量

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