Abstract: A capillary electrophoresis technique with electrochemical detection (CE-ED) for determination of tetracyclines (TC) and oxytetracycline (OTC) in eggs was described in this study. Effects of several factors, such as the pH value and concentration of running buffer, concentration of Tween-20, separation voltage, injection time and current potential applied to the working electrode, were investigated to find the optimum conditions. Well-defined separation of TC and OTC was achieved in the running sodium phosphate monobasic (pH 2.6). A carbon-disk electrode used as the working electrode exhibits good response at +1.20 V (vs. SCE(saturated calomel electrode)) for the analytes. The detection limits (S/N=3)for TC, OTC are 1.9×10-8 g/ml, 4.1×10-8 g/ml, respecratively.

Key words: tetracyclines, oxytetracycline, capillary electrophoresis