EFFECT OF UREA ADDITION IN MICELLAR ELECTROKINETIC CHROMATOGRAPHY

The addition of urea to a micellar solution was developed for the separation of hydrophobic compounds by micellar electrokinetic chromatography (MEKC). The logarithm of the capacity factor (k') decreased linearly with increasing concentration of urea. The use of a high concentration of urea allowed the MEKC separation of hydrophobic compounds, which were mostly included in the micelle and could not be resolved by conventional MEKC. The addition of urea also expanded the migration-time window and hence enhanced the resolution. The effect of urea is discussed from the standpoint of the contribution of urea to a diminished water structure around a hydrophobic solute. Two successful examples of the application of the technique are given for the MEKC separation of a complex mixture and hydrophobic compounds.