Determination of five macrolide antibiotic residues in milk by micellar electrokinetic capillary chromatography with field amplified sample stacking

The aim of this study is to develop a new micellar electrokinetic capillary chromatography with field amplified sample stacking for the determination of five kinds of macrolide antibiotic residues in milk. The main factors that affect the separation and enrichment of these analytes were optimized. The optimum running buffer was composed of 60 mM phosphate, 5 mM sodium cholate, and 1.0 mM cetyltrimethyl ammonium bromide at pH 7.0. The separation voltage was 20 kV and the sample was electrokinetically injected at 10 kV for 120 s. The detection wavelength was set at 195 nm. Under the optimized conditions, the enrichment factor of tilmicosin, erythromycin, clarithromycin, roxithromycin, and tylosin were 866, 565, 908, 702, and 675, respectively. The limits of detection ranged from 0.002 to 0.004 mg/kg. The method shall meet the requirement of their maximum residue limits ruled by China, the European Union, the United States, and other countries. Practical applicationsThe developed method has been applied successfully to the determination of the milk samples spiked at 0.05 and 0.1 mg/kg. The recoveries ranging from 72.8 to 93.7% demonstrate that the method can be applied to the detection of tilmicosin, erythromycin, clarithromycin, roxithromycin, and tylosin residues in milk.