A novel deep eutectic solvent based ultrasound-assisted liquid phase microextraction (DES-UALPME) has introduced for preconcentration of cobalt. Deep eutectic solvents (DESs) are studied as a green and eco-friendly solvents. In this method, 1-nitroso-2-naphthol was used as ligand. Cobalt concentration in DES rich phase was measured by a microsample injection system coupled with flame atomic absorption spectrometer (MS-FAAS). Under optimum conditions, LOD, LOQ preconcentration factor (PF) and % RSD were determined as 1.10 mu g L-1, 3.60 mu g L-1,15 and 7.1% respectively. The accuracy of the developed method was evaluated by the analysis of a pharmaceutical supplement and tea samples. Recoveries of certified reference materials and spiked samples were obtained in the range of 97-105%. Finally, the performance characteristics of the proposed method were compared with other liquid phase microextraction procedures. (C) 2016 Elsevier B.V. All rights reserved.