Stability of penicillin antibiotic residues in meat during storage -: Ampicillin

Incurred samples from a pig treated with ampicillin, one of the most important penicillin antibiotic drugs used food-producing animal treatments, were analyzed at the residue level of the drug in muscle tissue (approximate to 100 mu g kg(-1)) during their freezing storage and using three different techniques: quantitative microbiological assay, HPLC-UV and LC-MS. Two parameters have been specifically monitored: storage temperature (20 and -75 degrees C) and storage packaging (ground meat or bulk meat). No significant decrease was observed during the first 3 months of storage monitoring at -20 and -75 degrees C. On the contrary, the sample preparation significantly affected the drug concentration in muscle from the very beginning of the storage. Grinding the meat before storage allowed to keep the drug near the higher level of concentration (approximate to 100 mu g kg(-1)) when bulk meat stored frozen systematically led to a decreased value (approximate to 75 mu g kg(-1)). After 8 months of storage at -20 degrees C, a significant decrease arose and was never observed at -75 degrees C. All the results were similarly obtained with the three different techniques used simultaneously, which allows to indicate a good correlation between the techniques. (C) 2000 Elsevier Science B.V. All rights reserved.