||The main research of this thesis includes three sections. The purpose of first part is to develop a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of 8 macrolide antibiotics and lincosamides inside fish tissue, including erythromycin (ERM), oleandomycin (OLD), kitasamycin (KIT), tylosin (TYL), josamycin (JOS), spiramycin (SPM), tilmicosin (TIL), and lincomycin (LIN). Homogenized samples are first extracted with acetonitrile, dehydrated with sodium sulphate anhydrous, and then condensed. After the residue was redissolved in methanol and the extracts were partitioned with n-hexane to remove lipids, the sample is filterced and detected by LC/MS-MS using chromatography columns of Agilent HC-C18 (5μm, 150 mm ×4.6 mm). The mobile phase A was 5mM ammonium acetate containing 0.1% formic acid, while the mobile phase B was acetonitrile. The analysis of 8 macrolide antibiotics and lincosamides can be achieved within 10 minutes with electrospray ionization-tandem mass spectrometry in positive mode using multiple reaction monitoring (MRM) for simultaneous detection.|
The second part is to verify the method by regulation of European Union (EU) resolution scheme (2002/657/EC). In the case where the drug is set as allowed drug, the recovery rate under gradient addition according to MRL is between 93.64% to 106.67%, and the CV is between 0.27% to 7.17%. In the case where the drug is set as prohibited drug, the recovery rate under gradient addition according to MRPL is between 96.35%~104.88%, and the CV is between 6.77%~13.91%. As a result, the decision limit (CCα) and the Detection capability (CCβ) of the 8 macrolide antibiotics and lincosamides is between 0.24 to 0.40μg kg-1 and 0.33 to 0.49μg kg-1.
The last section is to evaluate the stability of drugs in fish body under domestic preservation and process methods on fish, including refrigeration at -20℃ and cold storage at 4 ℃. The test is implemented by adding the drug into fish tissue according to MRL and detecting the antibiotics residue after regulated 40 days. Besides, the effect on activity of drug residue in fish body after boiling at 100 ℃ is compared. The results show that the residual amount of spiramycin, josamycin, tilmicosin, and lincomycin is below 35% while that of erythromycin, oleandomycin, kitasamycin, and tylosin will be below 20%. Therefore, the drugs including erythromycin, josamycin, tylosin, and lincomycin will stay stably in fish tissue if they are stored under -20 ℃. However, it may affect human health if the fish contains such antibiotic residues is not boiled.