SOLUTE PARTITION STUDY IN AQUEOUS SODIUM DODECYL-SULFATE MICELLAR SOLUTIONS FOR SOME ORGANIC-REAGENTS AND METAL-CHELATES

The partition constants (K(d)) have been estimated for nitrophenols, thiazolylazo dyestuffs and metal chelate compounds into the sodium dodecyl sulfate (SDS) micellar phase at an ionic strength of 0.10 M [(H+, Na+)Cl-] and at 20-degrees-C. The equilibrium partition data obtained by batch-wise solution spectrophotometry (equilibrium shift method) agree well with those by the micellar electrokinetic capillary chromatography (MECC) with the SDS micellar pseudo-stationary phase. The MECC clearly discriminates a very small difference (0.03) in the log K(d) values of some metal chelates. The plot of the K(d) values with the van der Waals volume of the solute molecules obviously shows the leveling-off of the K(d) values over solute size near 110 ml/mol, which seems to be consistent with the results obtained in the Triton X-100 micellar system. This phenomenon arises most probably from the rigidity of the micellar pseudo-phase (a micellar volume-constraint effect) in sharp contrast with true two-phase partitioning such as solvent extraction systems.