In this article, we report the simultaneous determination cholesterol (CL), ascorbic (AA) acid and uric acid (UA) at a carbon paste electrode (CPE) modified with copper oxide decorated reduced graphene (CuO-rGR), with 1-methyl-3-octylimidazolium tetrafluoroborate (1M3OIDTFB) as a binder. The electrode, CuO-rGR/1M3OIDTFB/CPE, showed remarkable sensitivities towards the determination of the analytes, and well defined and clearly separated oxidation peaks were obtained during their simultaneous analysis in a buffer solution at pH 7.4. The differences observed between their peaks potentials are as follows: 430 mV (between CL and AA), 270 mV (between AA and UA) and 700 mV (between CL and UA). The morphologies and structure properties of the CuO-rGR were investigated by FESEMD and EDAX methods. The CuO-rGR/1M3OIDTFB/CPE displayed linear response in the concentration ranges 0.04-300.0 mu M, 0.04-240.0 mu M and 0.4-400.0 mu M for CL, AA and UA with the detection limits 9.0 nM, 9.0 nM and 0.08 mu M, respectively. The CuO-rGRI1M3OIDTFB/CPE displayed high performance for the determination of CL, AA and UA in real samples. (C) 2019 Elsevier Inc. All rights reserved.