For the first time, a novel electrochemical sensor; gold nanoparticles-coated poly(3,4-ethylene-dioxythiophene) polymer modified gold electrode in presence of SDS (Au/PEDOT-Au-nano...SDS) was developed by the electrodeposition of gold nanoparticles on poly(3,4-ethylene-dioxythiophene)(PEDOT) modified gold electrode for the selective determination of dopamine (DA) in presence of uric acid (UA) and ascorbic acid (AA) in presence of sodium dodecyl sulfate (SDS). Synergism between the composite of conducting polymer matrix and gold nanoparticles in presence of SDS for electron transfer enhancement of DA is explored. Electrochemical investigation and characterization of the modified electrode are achieved using cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron, and atomic force microscopies. The oxidation current signal of DA is remarkably stable via repeated cycles and has unique long term stability. Very small peak potential separation (Delta E-p), almost zero or 15 mV is also obtained by repeated cycles indicating unusual high reversibility. The use of SDS in the electrochemical determination of DA using linear sweep voltammetry at Au/PEDOT-Au-nano modified electrode resulted in determining DA at very low concentrations. The DA concentration could be measured in the linear range of 0.5-20 mu mol L-1 and 25-140 mu mol L-1 with correlation coefficients of 0.9978, and 0.9987, and detection limits of 0.39 nmol L-1 and 1.55 nmol L-1, respectively. The validity of using this method in the determination of DA in human urine was also demonstrated. It has been shown that modified electrode can be used as a sensor with high reproducibility, sensitivity, selectivity, and long term stability. (C) 2012 Elsevier Ltd. All rights reserved.