Effect of the dodecyl sulfate counterion on selectivity and resolution in micellar electrokinetic chromatography: II. Organic counterions

Various tetraalkylammonium ions, such as tetramethyl‐, tetrapropyl‐, tetrapentyl‐, and cetyltrimethylammonium, can be added to sodium dodecyl sulfate (SDS) micellar solutions to achieve unique selectivities in micellar electrokinetic chromatography (MEKC). The cetyltrimethylammonium/SDS buffer system showed the greatest increase in methylene selectivity, while both tetrapropylammonium/SDS and cetyltrimethylammonium/SDS buffer systems had the greatest selectivities for the solutes studied. In addition, the buffer systems that used symmetrical tetraalkylammonium ions showed reductions in retention specific for the carbonyl functional group. The tetramethylammonium/SDS buffer system had the best resolution due to both improved selectivity and an elution range that was 2.5 times that of a comparable SDS buffer system.