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

Background: The wide usage of tetracyclines in livestock farming 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 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. After the addition of NaCl (35% for eggs and 20% for chicken), a mixture of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and ethyl acetate (300 mu L-50 mu L for eggs and 200 mu L-60 mu L for chicken) was used as the extractant. After centrifugation, the extract was collected for HPLC analysis. Results: The developed method showed good linear relationships (10.0-500 mu g/kg), low method detection limits (0.219-1.42 mu g/kg) and quantification limits (0.731-4.72 mu g/kg), and 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 different parts of chicken. The contents of tetracyclines in all samples were lower than their maximum residue limits. Conclusion: 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 abilities. This method has been successfully applied to the analysis of six tetracyclines in eggs and chicken.