In the present work, CuO nanoparticle decorated on single wall carbon nanotubes (CuO/SWCNTs) nanocomposite was successfully synthesized by chemical precipitation method and used for modification of carbon paste electrode (CPE) in the presence of 1-butyl-3-methylimidazolium hexafluorophosphate (1-B-3-MIHFP) liquid as binder. The novel voltammetric sensor was used as first electrochemical sensor for determination of sulfisoxazole (SFX). CuO/SWCNTs nanocomposite characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) methods. Voltammetric methods such as cyclic voltammetry, square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS) and chronoamperometry were performed to assess the electrochemical performance of CuO/SWCNTsi1-B-3-MIHFP/CPE towards SFX in aqueous solution. The voltammetric obtained data confirm the significant enhancement of oxidation current and reduction overvoltage for electro-oxidation of SFX at a surface of CuO/SWCNTs/1-B-3-MIHFP/CPE. The square wave voltammetric response shows the linear increment of oxidation signals with an increase in the concentration of SFX in the range of 0.08-650 mu M with limit of detection 0.04 mu M. Using CuO/SWCNTs/1-B-3-MIHFP/CPE the SFX and folic acid peaks are separated ca. 0.72 and 0.895 V, respectively; hence SFX can be detected in the presence of folic acid. Finally, the CuO/SWCNTs/1-B-3-MIHFP/CPE was used as high sensitive tools for analysis of SFX and folic acid in real samples. (C) 2017 Elsevier Inc. All rights reserved.