Simultaneous Determination of Melamine, Ammelide, Ammeline and Cyanuric Acid in Milk Products by Micellar Electrokinetic Chromatography

Micellar electrokinetic chromatography (MEKC) was developed for the simultaneous determination of melamine, ammeline, ammelide and cyanuric acid on a fused silica column coated with poly (diallyldimethylammonium chloride). Separation was performed using 5 mM boric acid, 5 mM sodium tetraborate, 10 mM sodium dodecylsulfate and 2 mM tetrabutylammonium hydroxide at pH 9.15 as the background electrolyte, an applied voltage of +20 kV and UV detection at 210 urn. The four compounds were completely separated within 5.2 min. The detection limits of melamine, ammeline, ammelide and cyanuric acid were 0.10, 0.04, 0.03 and 0.08 mu g/mL, respectively. The relative standard deviations of retention times for melamine, ammeline, ammelide and cyanuric acid were 0.14, 0.29, 0.05 and 0.12%, and those of peak areas were 0.11, 0.36, 0.28 and 0.24%, respectively. The method was successfully applied to determine melamine and its derivative in milk samples. Before analysis, protein in milk sample was removed using HCl and the remaining matrix was cleaned up using Sep-Pak C18, which otherwise caused electrophoretic de-stacking. The results showed that melamine and cyanuric acid were found in UHT milk samples.