Determination of florfenicol in fish feeds at high inclusion rates by HPLC-UV.

This paper presents a modification of the HPLC-UV method for the determination of florfenicol in fish feed to allow its use for medicated feeds with inclusion rates as high as 6 g/kg. The work was undertaken to make the method, previously validated over a range from 0.2 to 4 g/kg, applicable to higher concentration medicated feeds required for certain warmwater species. Method validation experiments confirmed that the modified method is suitable for quantitation of florfenicol in fish feed over an expanded 0.2-6 g/kg range. Accuracy was evaluated by two analysts over a range of 4-9 g/kg (up to 150% of the highest incorporation rate). The average accuracy was 100.1% (SD 0.4%). The accuracy data were used to evaluate repeatability and intermediate precision (interday and analyst). Proof of performance was conducted by replicate analysis of samples taken from commercial scale batches of salmonid and catfish feeds medicated at 4 g/kg and 6 g/kg.