Unified procedure for the determination of antibiotics in animal feeds.

A new method was developed for the determination of antibiotics in animal feeds. This qualitative and quantitative method can be applied to 17 antibiotics currently accepted for use in animal feeds. A solvent prewash step is used to differentiate groups of antibiotics and individuals of the same class of antibiotics and to remove interfering substances. Agarose gel electrophoresis at pH 6.0 and 8.0 is used to further differentiate the individual antibiotics and as an agar diffusion assay. Minimum detectable concentrations of antibiotics currently accepted for use in animal feeds were determined against selected microorganisms.