Effects of tetraalkylammonium salts on the micellar electrokinetic chromatography of aniline and substituted anilines

Abstract

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 (TMA) ions results in increases in the elution range ( t mc− t 0) and the migration times for the aniline solutes. In contrast the addition of small concentrations of tetrabutylammonium (TBA) ions leads to changes in the elution order and a considerable improvement in the separation of the anilines without a significant increase in the elution range. Further increases in the concentration of TBA ions to levels above 1/3 the concentration of SDS narrows the elution range and has a detrimental effect on the separation. The effects of the TBA ions are attributed to changes in the structure of the SDS micelles resulting in a more open and disordered SDS micelle which enhances the transfer of anilines with polar ring substituents into the micelle.