Sakurai Takao, Kurata Shoji, Ogino Kenji
Criminal Investigation Laboratory, Metropolitan Police Department.
Anal Sci. 2016;32(2):129-33. doi: 10.2116/analsci.32.129.
The color-changing phenomenon of hydrophobic bisazo dye, Sudan III in an acetonitrile solution against the addition of concentrated sulfuric acid has been discovered and the chromic properties investigated. Based on observations, a novel quantification method of concentrated sulfuric acid has been developed. Sudan III changes its color from orange to blue against a small volume of sulfuric acid, and the acetonitrile solution of Sudan III is the most suitable for observing the color-change phenomenon. (1)H-NMR and UV-Vis spectroscopic studies showed that the color-change mechanism of Sudan III against sulfuric acid is due to the protonation of the dye by sulfuric acid. This phenomenon is applicable to the quantification of concentrated sulfuric acid by introducing the Hammett acidity function. The proposed method requires only a small amount of the sample, 0.04 mL, and enables rapid quantification.
发现了疏水双偶氮染料苏丹III在乙腈溶液中加入浓硫酸时的变色现象，并对其变色性质进行了研究。基于这些观察结果，开发了一种新的浓硫酸定量方法。苏丹III加入少量硫酸后颜色从橙色变为蓝色，苏丹III的乙腈溶液最适合观察这种变色现象。核磁共振氢谱（¹H-NMR）和紫外可见光谱研究表明，苏丹III与硫酸的变色机理是由于硫酸使染料质子化。通过引入哈米特酸度函数，这种现象可用于浓硫酸的定量分析。所提出的方法仅需0.04 mL少量样品，即可实现快速定量。
