A carbon paste electrode (CPE) modified by sodium dodecyl sulphate (SIDS) was used for the detection of K(3)Fe(CN)(6) and dopamine. Cyclic voltammetry (CV) demonstrated improved response of K(3)Fe(CN)(6) and dopamine sensor at SDS/CPE compared to bare CPE. The effect of SIDS concentration on the electrode quality also reveals that SDS formed a monolayer on a carbon paste electrode surface with a high density of negative charged end directed outside the electrode. On the formation of a SIDS monolayer, the structure of the electrode interface changed significantly and the electrode/solution interface was replaced by the SDS monolayer/solution interface. The detection limit for K(3)Fe(CN)(6) is 1 x 10(-4) M and dopamine 1 x 10(-7) M. (C) 2009 Elsevier B.V. All rights reserved.