EFFECT OF THE DODECYL-SULFATE COUNTERION ON SELECTIVITY AND RESOLUTION IN MICELLAR ELECTROKINETIC CHROMATOGRAPHY .2. ORGANIC COUNTERIONS

Various tetraalkylammonium ions, such as tetramethyl-, tetrapropyl-, t etrapentyl-, and cetyltrimethylammonium, can be added to sodium dodecy l sulfate (SDS) micellar solutions to achieve unique selectivities in micellar electrokinetic chromatography (MEKC). The cetyltrimethylammon ium/SDS buffer system showed the greatest increase in methylene select ivity, while both tetrapropylammonium/SDS and cetyltrimethylammonium/S DS buffer systems had the greatest selectivities for the solutes studi ed. In addition, the buffer systems that used symmetrical tetraalkylam monium ions showed reductions in retention specific for the carbonyl f unctional group. The tetramethylammonium/SDS buffer system had the bes t resolution due to both improved selectivity and an elution range tha t was 2.5 times that of a comparable SDS buffer system.