Abstract
In this thesis, a new high performance liquid chromatographic method with two detectors (HPLC-SFD-PDA) for the reliable identification, confirmation and quantification of sarafloxacin residues in muscle plus skin, liver, kidney and vertebra of gilthead seabream (Sparus aurata L.), has been developed. According to this method an acidified methanol tissue extract is subjected to sorbent extraction on a cation exchange cartridge. Sarafloxacin quantitative elution is done with an ammoniated methanol solution and after a partition step with n-hexane the final extract is evaporated to dryness, reconstituted in mobile phase and injected to the HPLC for fluorescence identification. The chromatographic conditions are the following: - Analytical column Zorbax SB-C18, 5 μm [250 mm x 4,6 mm] – Guard column Lichrospher RP – select b, 5 μm – Column temperature 60°C – Mobile phase 30% Acetonitrile:Methanol [3 + 2] v/v 70% Trifluoroacetic 0.1%, pH 2,15 – Flow rate 0,9 mL.min-1 – Final extract volume 1 ...
In this thesis, a new high performance liquid chromatographic method with two detectors (HPLC-SFD-PDA) for the reliable identification, confirmation and quantification of sarafloxacin residues in muscle plus skin, liver, kidney and vertebra of gilthead seabream (Sparus aurata L.), has been developed. According to this method an acidified methanol tissue extract is subjected to sorbent extraction on a cation exchange cartridge. Sarafloxacin quantitative elution is done with an ammoniated methanol solution and after a partition step with n-hexane the final extract is evaporated to dryness, reconstituted in mobile phase and injected to the HPLC for fluorescence identification. The chromatographic conditions are the following: - Analytical column Zorbax SB-C18, 5 μm [250 mm x 4,6 mm] – Guard column Lichrospher RP – select b, 5 μm – Column temperature 60°C – Mobile phase 30% Acetonitrile:Methanol [3 + 2] v/v 70% Trifluoroacetic 0.1%, pH 2,15 – Flow rate 0,9 mL.min-1 – Final extract volume 1000 μL - Autosampler’s temperature 15°C – Injection volume 20 μL – Pump mode Isocratic – Electronic counterbalance 100 – Attenuation S. - Measuring units mV - SFD wavelength settings λex ~ 278 nm & λem~ 450 nm - UV wavelength setting λmax ~ 280 nm. With the above conditions sarafloxacin is eluted form the chromatographic column at a retention time of 6,983 ± 0,008 min [n = 10]. This method was validated for specificity, linearity, accuracy, precision, sensitivity, and intra – inter assay precision. Linearity was very good in the concentration range from 2 – 320 μg/kg. The correlation coefficient was found to be 0,999998. Accuracy data suggested an mean overall recovery of 82,1 ± 4,2 [RSD = 5,1%] for muscle plus skin, 79,2 ± 1,9 [RSD = 2,4%] for liver, 79,1 ± 4,3 [RSD = 5,4%] for kidney and 76,1 ± 3,3 [RSD = 4,3] for vertebra. Precision data, expressed in percent relative standard deviation, ranged from 0,96 to 6,46% in all tissue analyzed. The sensitivity, which corresponds to the slope of the calibration standard curve, was determined by calculating the factors Resolution [Rs = 1,25], Tailing factor [Tf = 1,847583e + 000] and signal to noise ration [S/N = 2]. Intra-assay precision [within day], was determined by the relative standard deviation of the results obtained for 6 spiked samples at 40 μg/kg level [RSD = 2,3%]. Inter-assay precision [between day], was determined by the overall inter assay variability of the results obtained from 5 spiked samples at 5 different levels, five times each [RSD = 4,5%]. Finally, the detection limit [LOD] was 1 μg/kg in muscle plus skin tissue of the gilthead seabream. This HPLC method was used to monitor sarafloxacin concentrations in tissues of cultured gilthead seabream during a medication period of 5 days and for 4 days after the last in feed administration at the therapeutic dose of 10 mg/kg body weight/day for 5 consecutive days. Three experiments were conducted in seawater during spring, summer and winter. One pilot experiment at 19,7 ± 1,18°C with 3 seabreams per sampling point, followed by two large scale experiments, one at high temperature of 25,19 ± 1,4°C, one at low temperature of 17,83 ± 0,26°C with 10 seabreams per sampling point. From this study it was found that sarafloxacin residues in seabream tissues at three different temperatures are depleted rapidly and fall below the Maximum Residue Limit of 30 μg/kg in 48 hours after the last dosing day. Also, at 108 hours after the last dose sarafloxacin concentrations were close to the LOD – 1 μg/kg in all tissues analyzed. Gilthead seabream market samples coming from Greek fish farming industries were analyzed in order to investigate the presence of sarafloxacin residues. Sarafloxacin residues were not detected to any fish sample. Finally, withdrawal period form muscle plus skin of the farmed gilthead seabream was calculated and it was found to be 42,2 hours.
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