Solvatochromism Based on the Interaction between Azo Dyes and Hydrophobic Ions: Application to the Determination of Surfactants by Flow-Injection Spectrophotometry
التفاصيل البيبلوغرافية
العنوان:
Solvatochromism Based on the Interaction between Azo Dyes and Hydrophobic Ions: Application to the Determination of Surfactants by Flow-Injection Spectrophotometry
The phenomenon of color development of anionic azo dyes by changing microenvironments of the dyes was examined in an acidic aqueous medium. Methyl orange and its analogues were investigated. In the presence of anionic azo dyes, organic onium ions and nonionic surfactants brought about decreases in absorbance at wavelengths near 510 nm and increases in absorbance at wavelengths near 400 nm. Anionic surfactants (AS−) react with a hydrophobic quaternary ammonium ion (Q+) to form a stable ion association complex (Q+ · AS−), and the residual Q+ reacts with an azo dye to change the absorbance at about 400 or 510 nm. On the basis of such color change phenomena, spectrophotometric methods for the determination of various kinds of surfactants were developed. The methods were applied to the flow-injection technique.