[Microbiological method for the detection of antibiotic residues in meat using mixed-mode, reverse-phase and...

A microbiological method for screening of residual benzylpenicillin (PCG), oxytetracycline (OTC) and spiramycin (SPM) in meat using a single mixed mode, reversed-phase and cation-exchange cartridge was developed. A meat sample was extracted with 0.1 mol/mL pH 4.5 phosphate buffer and the extract was applied to a MCX cartridge. The cartridge was washed, and adsorbed antibiotic residues were eluted with acetonitrile for acidic fractions and acetonitrile containing 5% ammonia solution-0.1 mol/mL pH 4.5 phosphate buffer (9:1, v/v) for basic fractions. Each eluate was evaporated to dryness and the residue was dissolved in phosphate buffer to prepare test solutions for microbiological assay. When the diameter of the inhibition zone was more than 12 mm, the result was considered positive. In this method, the average recoveries of PCG at 0.05 microg/g, OTC at 0.1 microg/g and SPM at 0.2 microg/g were 70%, 92% and 84%, respectively. Tolerances of the three antibiotics were detected. All the results demonstrate that this method is simple, rapid and useful for screening of these three antibiotic residues in meat.