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Determination of Marbofloxacin Residues in Beef and Pork with an Enzyme-Linked Immunosorbent Assay

Sheng, Wei, Xia, Xunfeng, Wei, Keyi, Li, Ji, Li, Qing X., Xu, Ting
Journal of agricultural and food chemistry 2009 v.57 no.13 pp. 5971-5975
beef cattle, swine, food animals, beef, pork, antibiotics, antibiotic residues, food contamination, enzyme-linked immunosorbent assay, quantitative analysis, inhibitory concentration 50, detection, cross reaction, chemical structure, chemical concentration, animal tissue extracts, liquid chromatography, validity, mass spectrometry, detection limit
Marbofloxacin is a fluoroquinolone veterinary antibiotic. An indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed for the detection of marbofloxacin using polyclonal antibody. The half-maximum inhibition concentrations (IC50) and limit of detection (LOD, calculated as IC20) of the ELISA for marbofloxacin in phosphate buffer were 4.6 and 0.6 ng/mL, respectively. The assay showed little cross-reactivity with marbofloxacin structural analogues, except for ofloxacin (148%). Matrixes from the extracts of beef and pork muscle have shown a significant influence on the ELISA. Standard curves of ELISA for marbofloxacin in the extracts of the appropriate marbofloxacin-free control muscles were used in the analysis of marbofloxacin in the animal muscles without any cleanup. The average recoveries of intra- and interassay for marbofloxacin from fortified muscle samples, at five concentrations of 10, 50, 100, 500, and 1000 ng/g, were 87-93 and 84-95%, respectively. The LOD of this assay for marbofloxacin in real muscle extracts was 0.8 ng/mL. A survey of 55 animal muscle samples purchased from local markets by the ELISA was conducted, and marbofloxacin was detected in one of them at a concentration of 22 ng/g. This positive sample was validated by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) to be 28 ng/g of marbofloxacin.