| By using liquid chromatography-tandem mass spectrometry technology, a study on an accurate and efficient detection method of Roxithromycin and its application in the pharmacokinetics of soft-shell turtles were carried out for the evaluation of the quality and safety.1. An ultra high performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method for the determination of roxithromycin in soft-shell turtle was developed and the detection conditions were optimized. Six different kinds of extractants and five different kinds of extract pH were compared according to the extraction effect. Samples were extracted by ethyl acetate. pH value was adjusted to8.5by sodium carbonate and free lipid was eliminated by hexane. The limit of quantitation (LOQ) for roxithromycin was found to be0.1ng/mL. Under the conditions mentioned above, recoveries ranged from70.97to95.46%at levels of5to500ng/mL with relative standard deviation (RSD) were from3.90%to9.75%. 2. The uncertainty of the method of determination of Roxithromycin was investigated. It was found that the sources of uncertainty consisted of sampling, reconstitution and concentration determination. The uncertainty components and combined uncertainty were calculated. Under the spiked levels of5ng/ml, the combined uncertainty, expanded uncertainty and test result of method were0.2634ng/mL,0.5268ng/mL and4.77±0.5268ng/mL respectively.3. Pharmacokinetics of roxithromycin were studied in plasma, liver and muscle of soft-shell turtles. After oral administration at a dose of60mg/kg by7consecutive days of feeding, samples were taken at1h,2h,4h,8h,28h,48h,72h,120h after last feeding. The concentrations of roxithromycin were determined by high performance liquid chromatography (HPLC-MS/MS). The results showed that the peak times of concentrations in plasma, muscles, livers were2h,8h,8h with the peak concentrations of19.03μg/kg,5.130μg/kg,13.98μg/kg, respectively. According to3P97analysis, roxithromycin in plasma, liver and muscle followed two compartment model. Equations were as follows:Cplasma=40.21xe-0.8514t+1.471xe-0.1798t;Cmusclc=3.349xe-0.0816t+5.358xe-0.04430t;Clivcr=4.942xe-0.07221t+0.7362xe-0.006898t,The elimination half-life (T(1/2)β) of roxithromycin in plasma, muscle, liver in soft-shell turtle were38.55h,15.65h and100.5h and recommended withdrawal period was15days under the water temperature of25±2℃4. The metabolites and metabolic pathway of roxithromycin in the plasma in soft-shell turtle at2h and after24h after feeding were analyzed by mass spectrometry analysis. The results showed that two metabolites (erythromycin-oxime, N-mono-and didemethylated derivatives of roxithromycin) were detected after2h and3metabolites (erythromycin-oxime, N-mono-and didemethylated derivatives of roxithromycin and deseladinose-roxithromycin) were detected after24h. |
PDF Full Text Request