Quantitative analysis of colistin and tiamulin in liquid and solid medicated premixes by HPLC with diode-array detection

Colistin (COL) and tiamulin (TML) are antibiotics used in veterinary practice. Diseases in animals are usually treated by adding the drug (liquid and/or solid medicated premix) to animal feed. Two simple, inexpensive, and rapid methods have been developed for quantification of COL and TML in liquid and solid medicated premixes by HPLC with diode-array detection, on the basis of scanning in the UV range 200-380 nm. The wavelengths 206 and 208 nm were used for quantification of COL and TML, respectively. The total elution time was less than 15 min. When the applicability of the optimized method was tested by analysis of commercial feed premixes there was no interference from the matrix.