The article presents the results of the development of sample preparation method of muscle and parenchymal tissues for their further testing on trimethoprim residues by enzyme-linked immunosorbent assay using Trimethoprim test kits from Kwinbon Biotechnology (China), designed to analyze another target matrix, viz. honey. The results of the comparison of sample preparation methods with the use of different techniques of analyte extraction from tissues, with the established percentage of

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... n are presented. The most effective conditions are proposed: acetonitrile extraction using ultrasonic intensification, subsequent concentration of the analyte by evaporation, reconstitution of dried residue and degreasing. This approach makes it possible to determine trimethoprim residues in poultry tissues at the level of 5-10 μg/kg with an absolute recovery of about 75%. In accordance with the Decision of the European Commission 2002/657/EC, the validation of the proposed method was carried out taking into account the maximum permissible levels (MRL) of trimethoprim in the tissues of productive animals. The suitability of the method was confirmed on the basis of establishing of the main validation parameters for screening methods (technical threshold and cut-off factor) using control (pure) and spiked with a standard solution of trimethoprim at the level of ½ MRL samples of muscle and parenchymal tissues of broiler chickens. The main advantages of the developed technique are simplicity of performance, rapidity and cost effectiveness. The certainty of the results obtained using the developed method was verified using the confirmatory UPLC-MS/MS method. The article presents the results of a comparative study of pure samples of broiler chickens muscles and parenchymal tissues and spiked at the level of ½ MRL with a standard solution of trimethoprim. The developed screening technique of enzyme-linked immunosorbent assay is recommended for determination of residual amounts of trimethoprim in tissue samples and can be used for routine laboratory tests, as well as to study the withdrawal procedure of veterinary drugs based on this drug.