Background: Danofloxacin is a synthetic antibacterial agent with broad spectrum antibacterial
and antimycoplasmal activity which is widely used in aquaculture.
Methods: A UPLC (Ultra Performance Liquid Chromatography) method was developed and validated
for the determination of danofloxacin (Dano) and its major metabolite N-desmethyl danofloxacin (Ndesmethyl
Dano) in muscle plus skin tissue of European seabass (Dicentrarchus labrax) for the first
time. For the separation an analytical column UPLC BEH C18 2.1 × 5 mm (1.7 µm) was used with an
isocratic mobile phase consisting of MeOH-water acidified with formic acid (0.01%) (18:82; v/v) and
flow rate of 0.3 mL/min within 5.5 min. The detection was performed at 275 nm using a photodiode
array detector for both compounds. Examined fluoroquinolones were isolated from seabass muscle and
skin tissue by extraction with acidic ACN and further purification with the QuEChERS methodology.
Results: Recovery rates from muscle and skin tissue ranged between 90.2 and 101.2% for both compounds.
The detection limit of the method was estimated at 13.73 µg/kg for Dano, 18.32 µg/kg for Ndesmethyl
Dano, while the limits of quantification were 41.62 and 55.52 µg/kg, respectively. The developed
method was fully validated in terms of selectivity, linearity, accuracy, precision, stability and
sensitivity according to the European Union Decision 2002/657/EC.
Conclusion: The new developed and validated method can be readily applied to aqua cultured fish after
dietary administration of danofloxacin.