A feasible method of fabricating phthalocyanine sensor was developed by covalent attachment of cobalt tetracarboxylic acidchloride phthalocyanine (CoTCACIPc) onto a preformed 2-mercaptoethanol (2-ME) self-assembled monolayer (SAM) modified gold electrode (designated as CoTCACfPc-2-ME-SAM). The surface concentration of the CoTCACIPc was found to be 4.58 x 10(-10) mol/cm(2). The sensor gave a linear response to L-cysteine over the concentration range 0.28-20 mu M with a detection limit of 5 x 10(-7) M and best response time of 2 s. (c) 2005 Elsevier Ltd. All rights reserved.