The oxidative polymerization of aniline on composite 2B pencil graphite was accomplished in phosphoric acid (H3PO4) containing 0.06 M calcium phosphate (Ca-3(PO4)(2)). The shifting of three pairs of redox peaks by 250 mV to the negative direction has increased antioxidant capacity of polyaniline (PAni). This was realised through reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical in methanol. The phosphate medium prepared PAni was a strong reducing agent and radical scavenger. Additionally, it was twice more effective than the one prepared in chloride medium. (C) 2008 Elsevier Ltd. All rights reserved.