EFFECTS OF TETRAALKYLAMMONIUM SALTS ON THE MICELLAR ELECTROKINETIC CHROMATOGRAPHY OF ANILINE AND SUBSTITUTED ANILINES

Experiments investigating the effects of tetraalkylammonium (TAA)ions on the micellar electrokinetic chromatography (MEKC) of aniline and a series of 12 substituted anilines using sodium n-dodecyl sulfate (SDS) are reported. Increasing the concentration of tetramethylammonium (TM A) ions results in increases in the elution range (t(mc) - t(0)) and t he migration times for the aniline solutes. In contrast the addition o f small concentrations of tetrabutylammonium (TEA) ions leads to chang es in the elution order and a considerable improvement in the separati on of the anilines without a significant increase in the elution range . Further increases in the concentration of TEA ions to levels above 1 /3 the concentration of SDS narrows the elution range and has a detrim ental effect on the separation. The effects of the TEA ions are attrib uted to changes in the structure of the SDS micelles resulting in a mo re open and disordered SDS micelle which enhances the transfer of anil ines with polar ring substituents into the micelle. (C) 1998 Elsevier Science B.V.