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Electrophoretic properties of dodecyltrimethylammonium bromide micelles in KBr solution
Author(s) -
Sabaté Raimon,
Gallardo Montserrat,
Estelrich Joan
Publication year - 2000
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/(sici)1522-2683(20000201)21:3<481::aid-elps481>3.0.co;2-9
Subject(s) - microelectrophoresis , chemistry , aqueous solution , zeta potential , micelle , pulmonary surfactant , electrophoresis , counterion , critical micelle concentration , analytical chemistry (journal) , surface charge , charge density , ionic bonding , aggregation number , ionic strength , chromatography , chemical engineering , ion , organic chemistry , biochemistry , nanoparticle , engineering , physics , quantum mechanics
Charge in ionic micelles determines the trends of their stability and their practical applications. Charge can be calculated from zeta potential (ζ) measurements, which, in turn, can be obtained by Doppler microelectrophoresis. In this study, the electrophoretic properties of dodecyltrimethylammonium bromide (DTAB) in KBr aqueous solution (0—6 m M ) were determined by Doppler microelectrophoresis. At very low surfactant concentrations (up to 6 m M ), ζ potential was quite constant and due to the ionized monomers (DTA + ). Above 6 m M , ζ potential increased to a maximum at surfactant concentrations still below the critical micellar concentration (CMC). This increase could be explained by a formation of nonmicellar aggregates of DTAB. Then, above the CMC, ζ potential underwent an abrupt reduction, which was dependent qualitatively and quantitatively on KBr concentration, and which could be due to an increase of the number of counterions adsorbed on the micelle surface. Calculation of effective micellar charge from ζ potential gave the surface charge density. Comparing this value with the theoretical, obtained from geometrical considerations, a fraction of 0.29 of charged micellar headgroups was obtained when DTAB was in aqueous solution, which is consistent with the value obtained by conductivity measurements.