No abstract

An analytical method based on HPLC with MS/MS detection was developed and optimized in order to determine the most useful antibiotics (sulphonamides and tetracyclines) used in aquaculture. A simple extraction procedure, without any clean-up step, was evaluated in order to obtain maximum analyte recovery from ¢sh samples (Sparus aurata). A mixture of methanol:water 70:30 (v/v)11mL EDTA 0.1M was selected as optimum extractant solution. Because no matrix e¡ects were observed, a standard calibration curve prepared in mobile phase was used for quanti¢cation purposes. Antibiotic-free ¢sh samples were spiked at di¡erent concentration levels and analysed by the optimized HPLC method. The average recoveries (n 5 6) obtained were satisfactory, ranging from 88% to 110% at 100 mg kg À 1 . The proposed methodology provided limits of detection for the tested antibiotics in the 1.2^16 mg kg À 1 range, lower than 100 mg kg À 1 , the maximum residue level established by the European Union. Finally, commercial ¢sh samples from di¡erent origins were analysed in order to con¢rm the usefulness of the developed methodology.

No abstract

An indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed in plate to detect three sulfonamide residues (sulfamerazine (SMR), sulfadimetoxine (SDM), and sulfadiazine (SDZ)) in gilthead sea bream (Sparus aurata) samples. Different extraction methodologies--using methanol/water 1:1 (v/v) + ethylene diamine tetraacetic acid (EDTA) 0.5% (m/v), acetonitrile, phosphate-buffered saline (PBS) 10 mmol L(-1) pH 7 and acetate buffer 100 mmol L(-1) pH 5--and cleanup steps, based on solid-phase extraction (C(18), SCX, Si) or liquid extraction with hexane, were assayed. As optimum, a fast and simple method using acetonitrile was selected to extract the sulfonamide residues from the edible muscle of fish. Due to matrix effects, a standard addition calibration curve in fish extract is necessary for quantification purposes. Sulfonamide-free samples were spiked at different concentration levels (between 30 and 90 ng g(-1), 5-15 ng mL(-1) in plate) and average recoveries (n = 8), ranging from 71% to 95%, 65% to 79%, and 72% to 95%, were obtained for SMR, SDM, and SDZ, respectively. The assay detection limits for these antibiotics were lower than 100 microg kg(-1) (maximum residue level established by the European Union). The accuracy was evaluated by spiking blank fish extracts at different concentrations (10-40 ng mL(-1), 5-20 ng mL(-1) in plate), and the relative errors ranged between +/-20%. Finally, in order to confirm the utility of the developed ELISA as a screening methodology, fish samples from different supermarkets were analyzed, and results were compared with those obtained by a validated high-performance liquid chromatography (HPLC) method. The correlation between the results obtained by both ELISA and HPLC methods is satisfactory.

No abstract