A study of dye-surfactant interactions. Part 2. The effect of purity of a commercial cationic azo dye on dye-surfactant complex formation.

The interactions between the cationic azo dye C.I. Basic Yellow 25 and the cationic surfactant cetylpyridinium chloride have been studied by potentiom etry, UV/VIS spectrophotometry and H-1 NMR. The effect of the purity of the commercial sample of the dye on the dye-surfactant interactions has been i nvestigated. The results show that the cetylpyridinium chloride forms a com plex with one of the components of the commercial sample of the dye in aque ous solution. The concentration of this component is decreased by purificat ion of the commercial dye sample. The results also indicate that there are no dye-surfactant interactions in solutions of the cationic and nonionic co mponents of the dye. According to this observation, we conclude that the su rfactant cetylpyridinium chloride does not form a complex with the dye comp onent in the commercial sample of C.I. Basic Yellow 25, and that the reduct ion of the free surfactant cation concentration in the solution causes redu ction of the levelling action of the surfactant in the system involving the same charged dye and surfactant. (C) 1998 Elsevier Science Ltd. All rights reserved.