Electromotive force studies about some dyes-cationic surfactants interactions in aqueous solutions

The interactions of Orange II and Direct Red 80, anionic azo dyes, and also Indigocarmine with n-dodecyltrimethylammonium bromide (DTAB) and hexadecyltrimethylammonium bromide (HTAB) in submicellar concentration ranges have been investigated by a potentiometric technique using DTAB and HTAB membrane selective electrodes. The detection limits for HTAB and DTAB electrodes are 8 × 10−7 and 5 × 10−7 mol dm−3, respectively. The data show that significant binding takes place and the critical concentrations associated with the saturation of the dyes with bound surfactant have been determined. It has also been shown that free micelles occur in solution before the dyes become fully saturated with bound surfactant. The results also show that under the same experimental conditions the complex formation between HTAB and Orange II takes place at more less surfactant concentration than between DTAB and Orange II. EMF data and comparison between calibration and binding curves showed that interaction between HTAB and Orange II is more than that between Direct Red 80 and Indigocarmine.