Comparative Studies of Feed Samples on Salinomycin Contamination using Screening and Confirmatory Methods

The article presents the results of development of feed samples preparation method for further testing on salinomycin residues by ELISA using Salinomycin ELISA test kit, manufactured by Beijing Kwinbon Biotechnology (China) for another target matrix: tissues and eggs. Comparative study by means of different extractants and conditions of analyte extraction from feed was carried out, and recoveries’ percentages were established. Optimal conditions for two-stage extraction with methanol saline solution followed by ethyl acetate extraction from alkaline medium were experimentally selected; with further analyte concentration by evaporation and dry residue reconstitution. Application of this technique makes it possible to determine salinomycin residues in feed samples at the level of 0.35 - 0.70 mg/kg with absolute recovery of ~ 70 %. Suitability of the method was confirmed by comparative study of actually contaminated feed samples, performed by two screening methods: ELISA and TLC, and confirmatory method UHPLC-MS/MS. Developed technique has main advantages: it is simple, rapid and cost effective. Elaborated ELISA method is recommended for salinomycin residues determination at the level of cross-contamination on feed production and can be utilized in routine laboratory tests to prevent economic losses, caused by mortality of poultry and non-target animals, and to prevent salinomycine residues accumulation in food.