An effective approach for the sample pretreatment of solid food samples based on the use of three-component deep eutectic solvent (quaternary ammonium salt, carboxylic acid and medium chain fatty acid) was developed. Each component of deep eutectic solvent played a key role for separation of target analytes from solid-phase sample and their preconcentration based on dispersive liquid–liquid microextraction. The approach was applied for the HPLC-UV determination of sulfamethazine and sulfamethoxazole in chicken meat samples. The effect of deep eutectic solvents composition on the efficiency of both sample pretreatment steps was investigated. It was found that the solvent based on tetrabutylammonium bromide, malonic acid and hexanoic acid (1:1:1, mol/mol) provided the most effective separation and preconcentration of sulfanilamides. The procedure included mixing of solid food sample and deep eutectic solvent. By this sample pretreatment step, sulfanilamides were extracted into the solvent phase. For preconcentration of sulfanilamides, aqueous phase was injected into the deep eutectic solvent phase, resulting in its decomposition and the formation of hexanoic acid dispersed in aqueous phase. After phase separation, hexanoic acid phase containing sulfanilamides was withdrawn for HPLC-UV analysis. Under optimal conditions, the limits of detection calculated from a blank test based on 3σ were 3 µg kg⁻¹ and 7 µg kg⁻¹ for sulfamethoxazole and sulfamethazine, respectively.