A deep eutectic solvent ultrasound-assisted emulsification microextraction (USAEME-DES) procedure for the separation and preconcentration of quercetin in vegetable and fruit samples has been established. An alcohol-based extraction has been applied as sample pre-treatment step prior to microextraction procedure. Quercetin was extracted into DES phase (tetrabutylammonium chloride: decanoic acid (TBACI-DA, 1:3 M ratio) and analyzed by UV-VIS spectrophotometry at 370 nm. For the quantitative recoveries of quercetin, optimal pH, sample solution volume, volume and kind of DES, and ultrasonication time were 3.0, 15 mL, 250 mu L. of 1:3 M ratio of TBACI-DA acid and 5 min, respectively. The influences of matrix constituents were also studied. The developed method has a limit of detection (LOD) of 18.8 mu g L-1 and a relative standard deviation (RSD) of 5.1%. The developed procedure was applied to analysis of vegetable and fruit samples, which prepared by alcohol based extraction step. (C) 2019 Elsevier B.V. All rights reserved.