Determination of oxolinic acid in faeces and urine of turbot (Scophthalmus maximus) by high-performance liquid chromatography using fluorescence detection

A procedure for the determination of oxolinic acid (OA) in faeces and urine of turbot (Scophthalmus maximus), using reversed-phase high-performance liquid chromatography is described. Liquid chromatography was performed on a 5-μm PuroSpher RP-18E® cartridge using acetonitrile and 0.001 M aqueous orthophosphoric acid solution as mobile phase, with fluorescence detection. After the addition of an internal standard, oxolinic acid was extracted by using a liquid–liquid extraction procedure. Linearity and precision were checked over the concentration ranges 1.0–1000 μg/g (faeces) and 0.06–10.00 μg/ml (urine). Limits of detection of OA in faeces and urine were 0.20 μg/g and 0.02 μg/ml respectively. Mean extraction recoveries of OA from faeces and urine were 102.0 and 91.6% respectively.