SPECTROPHOTOMETRIC STUDY OF THE EFFECT OF UNIVALENT ELECTROLYTES ON CRITICAL MICELLE CONCENTRATIONS OF [1-(ETHOXYCARBONYL)PENTADECYL]TRIMETHYLAMMONIUM, 1-HEXADECYLPYRIDINIUM, AND DIMETHYLBENZYLDODECYLAMMONIUM BROMIDES

Critical micelle concentrations of three antimicrobial cationic surfac tants, i.e. quaternary ammonium salts [1-(ethoxycarbonyl)pentadecyl]tr imethylammonium bromide, 1-hexadecylpyridinium bromide, and dimethylbe nzyldodecylammonium bromide were determined by UV spectrophotometry in aqueous solutions. In the case of the first two compounds, the effect of addition of strong electrolytes KF, KCl, KBr, Kl, KSCN, and LiCl, respectively, on the decrease of CMC was also followed. The results we re processed in the form of a logarithmic dependence of CMC on the tot al concentration and the effect of both anions and cations of the adde d electrolyte was discussed. The UV spectrophotometry appeared to be a useful tool for the determination of CMC's of the order 10(-3) mol dm (-3) or smaller, if the micellizing surfactant cations or at least the corresponding counterions (in this work Br- and l(-)) exhibited conve nient spectral parameters.