Novel poly(hexylmethacrylate) carbon composite electrodes have been prepared from graphite powder and poly(hexylmethacrylate) binder, and modified with Keggin-type polyoxotungstate anions in the form of tetra-n-butylammonium (TBA) hybrid salts. The salts used were the lacunary anion compound, [(C(4)H(9))(4)N](4)H(3)[PW(11)O(39)], and the metal substituted [(C(4)H(9))(4)N](4)H[PW(11)Co(II)(H(2)O)O(39)]center dot H(2)O Carbon composite electrodes without poly(hexylmethacrylate) were also prepared for comparison. The electrochemical features of the polyoxoanions were maintained after immobilization. The influence of scan rate and pH on the voltammetric characteristics of the first tungsten reduction process of the immobilized polyoxometalates led to the conclusion that the process was diffusion-controlled, depending on the uptake of protons from solution. The chemically modified electrodes were stable and their preparation was easy to perform, their good stability being related to the insolubility of the hybrid salts in aqueous solution, and to the affinity of TBA towards the pasting liquid. This new modification using poly(hexylmethacrylate) also slightly improves the current sensitivity. In the absence of polyoxometalates, the peak current for the hexacyanoferrate redox couple is significantly higher when poly(hexylmethacrylate) binder is used. (C) 2009 Elsevier B.V. All rights reserved.