This article details electrochemical investigations of carbon paste electrode (CPE) modified with electroactive polyimide (EPI) as ascorbic acid sensor (vitamin C. AA). EPI, with aniline-pentamer-based in the main chain, was synthesized from oligoaniline and p-phenylenediamine by oxidative coupling polymerization. The well-defined molecular structure of the oligoaniline and EN was confirmed by LC-Mass, H-1 NMR and FTIR spectroscopy. The in-situ chemical oxidation of the reduced form of soluble, electroactive poly(amic acid) (EPAA) in N-methyl-2-pyrrolidone was monitored by UV-Visible absorption spectra. Moreover, the electroactivity of the EPAA and EPI were evaluated by performing electrochemical cyclic voltammetry studies. A linear relationship between the concentration of AA added and the change of peak current obtained, as shown by the linear calibration curve of the amperometric response of the CPE modified with EPI sensor to the concentration of AA (R-2 = 0.996, n = 15). The limit of quantitation measured was 32.2 mu M and the limit of detection for the EPI CPE was estimated 9.6 mu M at signal/noise (S/N) of 3. 2012 Elsevier Ltd. All rights reserved.