Determination of Six Tetracyclines in Eggs and Chicken by Dispersive Liquid-Liquid Microextraction Combined with High-Performance Liquid Chromatography.

BACKGROUND The wide livestock usage of tetracyclines may result in drug residues in foods. Therefore, it is necessary to develop reliable methods for the determination of tetracyclines in foods. OBJECTIVE A dispersive liquid-liquid microextraction (DLLME) combined with high-performance liquid chromatography (HPLC) method was developed for the analysis of six tetracyclines in eggs and chicken. METHODS After deproteinization, tetracyclines in acidic solutions were concentrated by vortex-assisted DLLME. Followed by the addition of NaCl (35% for eggs and 20% for chicken), a mixture of ionic liquid [Bmim]PF6 and ethyl acetate (300 μL-50 μL for eggs and 200 μL-60 μL for chicken) was used as the extractant. After centrifugation, the extract was collected for HPLC analysis. RESULTS The developed method showed good linear relationship (10.0-500 μg/kg), low method detection limits (0.219-1.42 μg/kg) and quantification limits (0.731-4.72 μg/kg), satisfactory relative recoveries (87.1-104%) with intra-day and inter-day RSDs in the ranges of 0.853-8.62% and 1.65-11.8%, respectively. The established method was successfully applied for the determination of six tetracyclines in eggs and chicken of different parts. The contents of tetracyclines in all samples were lower than their maximum residue limits. CONCLUSIONS A DLLME-HPLC method has been developed for the analysis of six tetracyclines in animal derived foods using ionic liquid and ethyl acetate as the extractant. HIGHLIGHTS The developed method is simple, sensitive, cost-effective and has strong anti-interference ability. This method has been successfully applied to the analysis of six tetracyclines in eggs and chicken.