Simplified liquid-chromatographic determination of residues of tetracycline antibiotics in eggs

A high-performance liquid chromatographic (HPLC) procedure is described for the identification and quantification of residues of tetracycline antibiotics (TCA) (oxytetracycline, tetracycline, chlortetracycline, and doxycycline), in eggs. Spiked and blank samples were prepared by homogenization with 1:1 (v/v) acetonitrile-mixed Mcllvaine buffer and EDTA solution (pH 4.0) then centrifugal ultrafiltration. HPLC was performed on a reversed-phase column with acetonitrile-5% (v/v) aqueous acetic acid, 35:65 (v/v), as mobile phase and photo-diode array detection. Average recoveries (each drug spiked at 0.1, 0.2, 0.3, 0.5, and 1.0 mug g(-1)) were greater than or equal to 77% with standard deviations (SD) between 1.5 and 3.5%. The inter-assay variabilities and their SD were <3.4% and <0.7%, respectively, and intra-assay variability was between 2.0 and 3.9%. The limits of quantitation (LOQ) were 0.064, 0.087 0.121, and 0.131 mug g(-1) for OTC,TC, CTC, and DC, respectively. The total time required for the analysis of one sample was less than 30 min.