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Color Change of Sudan III Against Concentrated Sulfuric Acid in Acetonitrile and Quantification for a Small Amount of Concentrated Sulfuric Acid

Color Change of Sudan III Against Concentrated Sulfuric Acid in Acetonitrile and Quantification for a Small Amount of Concentrated Sulfuric Acid

Takao Sakurai, Shoji Kurata, Kenji Ogino

Anal Sci. 2016;32(2):129-33.

PMID: 26860554

Abstract:

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.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1014689178	Sudan III-(naphthyl-d6)		1014689-17-8	Price

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