フラフラールを用いる2-プロパノールの比色定量法の改良
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概要
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According to the conventional colorimetric method for 2-propanol it is oxidized to acetone with K_2Cr_2O_7-H_2SO_4 solution, and the resulted acetone is allowed to be reacted with furfural to form difurfurylidene-acetone. However, a distillation process is unavoidable for this method to get rid of the color of Cr(VI) used as the oxidizing reagent. Therefore, if KMnO_4 is substituted for as the oxidizing reagent, more suitable colorimetric determination of 2-propanol should be accomplished, because permanganate will be easily decomposed by sodium sulfite. It was also found that the oxidation reaction of 2-propanol to acetone became accelerated by aldehyde compounds such as acetaldehyde-ammonia ([CH_3,CH(NH_2)_2OH]_3). Based on these observations, the following procedure was developed for the colorimetrie determination of 2-propanol with furfural. Take a sample solution (5ml) containing (2〜50)μg (CH_3)_<2-> CHOH. Add 0.3ml of 0.25M sulfuric acid, 0.3ml of 0.2 w/v% acetaldehyde-ammonia solution, and 0.3ml of 1 w/v% KMnO_4 solution. Leave it at room temperature after swirling the mixture for 60 min. Add 0.5ml of 1.5 w/v% sodium sulfite solution to destroy an excess of KMnO_4. Add 0.5ml of 1,2-cyclohexanediamine tetraacetic acid (CyDTA) solution which is prepared by dissolving 2.0g of CyDTA in 15ml of 12 w/v% sodium hydroxide solution and diluting the mixture with water to 100ml. Swirl. Stand for 1 min. Add 1ml of 12 w/v% sodium hydroxide solution and 0.5ml of furfural solution which is prepared by dissolving 1.0ml of furfural in 10ml of ethanol and then diluting the mixture with water to 100ml. Swirl the mixture, and leave ic at room temperature for 60 min. Add 9ml of 2:1 sulfuric acid. After standing for 20 min.measure the absorbance at 520nm against the reagent blank. The calibration curve was linear in the range of(2〜50)μg 2-propanol/5ml. An absorbance of solution at 520nm was 0.52 for 40μg 2-propanol/5ml, the coefficient of variation being 3.2%. Acetone, isobutyl alcohol and isopentyl alcohol yielded a positive interference, while methanol and benzyl alcohols negatively interfered with the determination.
- 社団法人日本分析化学会の論文
- 1978-12-05
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