Liquid chromatographic determination of sodium salinomycin in feeds, with post-column reaction

A method for the detection and quantitation of sodium salinomycin in feeds by a liquid chromatographic, post-column reaction system is presented. Sodium salinomycin is leached from feed with hexane, isolated as a dried residue, and dissolved in mobile phase for analysis. The drug is separated from interfering substances on a silica LC column, combined with vanillin reagent in a mixing tee, reacted with vanillin at elevated temperature in a coil, and detected in the effluent stream at 527 nm. Response, as peak area, is linear with concentration. Feed components, other common veterinary drugs, and closely related compounds do not interfere. Average recovery and coefficient of variation (CV) values for liquid spiked feeds and supplements were 101 +/- 3.5% and 100 +/- 0.3%, respectively. Results for laboratory blends and commercial scale feeds were within 6% of intent with CV values ranging from 0.4 to 5.1%.