Amphenicols stability in medicated feed – development and validation of liquid chromatography method

A liquid chromatography-ultraviolet detection method for the determination of florfenicol (FF) and thiamphenicol (TAP) in feeds is presented. The method comprises the extraction of analytes from the matrix with a mixture of methanol and acetonitrile, drying of the extract, and its dissolution in phosphate buffer. The analysis was performed with a gradient programme of the mobile phase composed of acetonitrile and buffer (pH = 7.3) on a Zorbax Eclipse Plus C18 (150 × 4.6 mm, 5 μm) analytical column with UV (λ = 220 nm) detection. The analytical procedure has been successfully adopted and validated for quantitative determination of florfenicol and thiamphenicol in feed samples. Sensitivity, specificity, linearity, repeatability, and intralaboratory reproducibility were included in the validation. The mean recovery of amphenicols was 93.5% within the working range of 50-4000 mg/kg. Simultaneous determination of chloramphenicol, which is banned in the feed, was also included within the same procedure of FF and TAP stability studies. Storing the medicated feed at room temperature for up to one month decreased concentration in the investigated drugs even by 45%. These findings are relevant to successful provision of therapy to animals.