Initial experiments aimed at separating povidone. caprolactam. melamine and urea. Melamine is a polar and weak basic compound (pKa-5-5.6) [18] while e-caprolactam is a very weak acid being negatively charged at extremely high pH values. Urea on the other hand is a very weak base being charged at acidic pH values. This means that zone electrophoretic separation of these solutes under eithe acidic or alkaline conditions is not possible. Therefore. SDS as micellar agent was added to the BGE to perform the separation by SDS-micellar electrokinetic chromatography (MEKC). MEKChas demonstrated to be a highly efficient technique for the separation of complex samples [19]. The SDS micelles migrate to the anode and interact with the solutes, being neutrally charged at the sepa ration conditions, mainly by hydrophobic interactions. To enhance the velocity of the solutes and thereby reducing analysis time, the separations of the solutes were investigated at neutral or higher pH values, where the EDF is sufficiently strong to sweep the negatively charged solute-SDS complexes towards the cathode. The counter current flow of the EDF and the SDS micelles improves the sepa- ration. Different background electrolytes including 100 and 50 mM phosphate buffer (pH 6.9-7.1) with varying SDS concentrations. i.e. 25-69mM, and 50 miM Tris-buffer (pH 9.0) with 52 mM SDS were investigated Experimental results showed that separation of povidone and melamine was not possible when using SDS-containing Tris buffer. However, a buffer system consisting of 50 mM phos phate buffer at neutral pH containing 69 mM SDS was chosen to perform MEC analyses since it gave good separation in a rea- sonable time. Fig. 2. The relatively high SDS concentration was necessary to baseline separate povidone and melamine which migrated close to each other. Paracetamol was selected as an internal marker since paracetamol. as a very weak acid. eluted between melamine and e-caprolactam. The interaction between the solutes and the SDS micelles increased in the order of caprolactam paracetamol melamine povidone> urea. Fig. 2. In order to further enhance the separation of melamine and povidone the column temperature was adjusted to 22