Abstract: The hydrophilic monolithic column was prepared in 100 μm i.d. capillary in situ using ethylene dimethacrylate as crosslinker, butyl methacrylate and 3-［dimethyl-［2-(2-methylprop-2-enoyloxy)ethyl］azaniumyl］propane-1-sulfonate as monomers. In the study, the hydrophilic interaction behavior of the monolithic column was demonstrated. The application of the column in pressurized capillary electrochromatography (pCEC) for the separation of melamine with ultraviolet detection has been studied. The effects of the composition of mobile phase, pH value, the concentration of the buffer, the flow rate of pump and voltage were investigated. The optimum separation for melamine was achieved with the mobile phase of 10 mmol/L phosphate buffer (pH 3.0) and acetonitrile (20:80, v/v), voltage at 3 kV and UV detection at 215 nm. The limits of detection (LODs) (S/N=3) for melamine standard was 0.05 mg/L. The method is simple, accurate and works well without using the ion-pairing agent. The powdered milk and liquid milk were analyzed quantitatively by pCEC using the hydrophilic interaction monolithic column. It is shown that this method is promising in the routine analysis of melamine in dairy products.

Key words: dairy products , melamine, preparation, pressurized capillary electrochromatography (pCEC), hydrophilic interaction capillary monolithic column