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Investigation of enrofloxacin residues through enzyme-linked immunosorbent assay and liquid cromatography-tandem mass spectrometry in eggs from laying hens after treatment

Enrofloxacin is one of the most used antibiotics in the poultry industry and the deposition of residues in poultry products, such as eggs, are of great concern to public health. In Brazilian law there is no standard withdrawal period for enrofloxacin in eggs and there is no Maximum Residue Limit (MRL) established for this antimicrobial in eggs. In this study, (Bioo Scientific(r)) commercial ELISA kit and LC-MS/MS were used to investigate enrofloxacin in eggs of 30 hens pretreated via drinking water at 10mg/kg of enrofloxacin for five days. Six eggs were collected daily and analyzed during treatment and after the end of treatment, for 15 days. Residues obtained maximum levels on the fifth day of treatment, declined gradually and were no longer detected from the ninth day to the end of treatment. Based on the MRL of 100mg/kg established for edible tissues of poultry by Brazillian law and for muscle, fat and skin, by the European Union, after six days of treatment withdrawal, the residue levels were below that limit, with the average of 37.43mg/kg in LC-MS/MS and 14.731mg/kg in ELISA. Within the conditions of this study, a withdrawal period of six days would be more appropriate to use the eggs for human consumption. The values obtained by ELISA for residues in eggs were lower than those obtained in LC-MS/MS for the same sample, however both methods showed statistical agreement. LC-MS/MS is the recommended method by Brazilian legislation for analysis of residues in food, however, according to the results the ELISA kit used can also be applied to the detection of enrofloxacin residues in eggs, with the advantages of speed and simplicity.

enrofloxacin; residues; eggs; LC-MS/MS; ELISA

Universidade Federal de Minas Gerais, Escola de Veterinária Caixa Postal 567, 30123-970 Belo Horizonte MG - Brazil, Tel.: (55 31) 3409-2041, Tel.: (55 31) 3409-2042 - Belo Horizonte - MG - Brazil