Veterinary antimicrobials and antiparasitics in fee-fishing ponds: analytical method and occurrence^*

The aim of this work was to develop and validate a method using online solid-phase extraction and ultra-high-performance liquid chromatography coupled to tandem mass spectrometry to determine residues of 22 veterinary drugs including sulfonamides, amphenicols, fluoroquinolones, benzimidazoles, trimethoprim (TMP) and oxytetracycline (OTC) in water from fee-fishing ponds. The optimal analytical conditions were as follows: XBridge C8 SPE column, Acquity UPLC CSH C18 analytical column, sample loading with water:methanol (98:2, v/v), mobile phase of water with 0.1% acetic acid:methanol (with gradient elution) and eluent flow rate of 0.3 mL min⁻¹. Quantification was performed in selected reaction monitoring mode and sulfadimethoxine-d₆, ciprofloxacin-d₈, florfenicol-d₃ and albendazole-d₃ were used as internal standards. Water samples collected from 11 fee-fishing ponds showed the presence of residues of FF (0.42–0.74 µg L⁻¹), albendazole (0.05–0.31 µg L⁻¹) and thiabendazole (0.45 µg L⁻¹). Thiamphenicol and TMP were detected at concentrations lower than the limits of quantification of the method (0.1 and 0.001 µg L⁻¹, respectively).