This work describes the electrochemical properties of cobalt tetra-aminophthalocyanine (CoTAPc) complex electropolymerized at the surface of multi-walled carbon nanotube (MWCNT) abrasively immobilized onto a basal plane pyrolytic graphite electrode (BPPGE). The constructed electrode displayed excellent electrocatalytic behaviour towards the oxidation of the herbicide, asulam, as evidenced by the enhancement of the oxidation peak current (similar to 6 times) and the shift in the oxidation potential to lower values (by similar to 120mV) in comparison with the bare BPPGE. The chronoamperometric detection of asulam which was carried out in 0.10 M phosphate buffer (pH 7.0) at a fixed potential of 0.65 V (versus Ag vertical bar AgCl) yielded excellent analytical parameters; a linear concentration range of 4.5-20 mu M, a sensitivity of 241 X 10(-3) mu A/mu M, a detection limit of 1.15 mu M asulam (using the Y-B + 3 sigma criterion) and a response time of similar to 2 s. (c) 2006 Elsevier Ltd. All rights reserved.