Cysteine is covalently bound to carbon nanoparticle surfaces (Emperor 2000 (TM), Cabot Corp., with sulfonate groups, ca. 9 to 18 nm diameter). Based on FTIR spectroscopic observations it seems the SH group is involved in the bonding to the CNP surface. The cysteine functionalized carbon nanoparticles are employed for the extraction and electrochemical determination of dopamine. The significant increase in voltammetric responses for pre-adsorbed dopamine compare with those for solution confirms high affinity of dopamine to carbon nanoparticles functionalized with cysteine (possibly due electrostatic interaction and hydrogen bonding between dopamine and cysteine at the surface carbon nanopartides). To obtain the optimum of adsorption conditions, the effects of pH, agitation rate, and adsorption time are investigated. A Linear calibration curve is obtained for dopamine in the range of 1.0 x 10(-8) to 1.0 x 10(-5) mol L-1 and the limit of detection is estimated 3.6 x 10(-9) mol L-1. The effect of co-existing species such as ascorbic acid and uric acid on the determination of dopamine was investigated. Finally, the determination of dopamine in human serum is demonstrated. (C) 2014 Elsevier Ltd. All rights reserved.