Novel cork-graphite electrochemical sensor for voltammetric determination of caffeine

Abstract Cork powder and granules are the major sub-products of the cork industry, which is an important economic activity in Portugal and other Mediterranean countries. Currently, many applications have been envisaged for this natural material, therefore, in this communication, for first time, a novel electrochemical sensor has been successfully prepared and tested based on cork and graphite. The device construction was performed by using cork and graphite in a mass ratio of about 50 and 70%. Cork-graphite electrode was characterized in terms of its surface morphology and electrochemical properties. The electrochemical sensor was tested for the determination of caffeine in real samples. Caffeine oxidation peak appeared at +1.51 V (vs. Ag/AgCl) in acidic solution at graphite and cork-graphite electrodes. However, cork-graphite electrode in a mass ratio of 70% showed the better sensibility for determining caffeine in aqueous solutions. A linearly relationship of current peak and caffeine concentration was achieved up to 1000 μM, with a limit of detection (LOD) of about 2.94 μM. Additionally, the caffeine concentrations estimated in drugs and soft drinks, using cork-graphite sensor at 70% of cork, were very similar to those obtained by HPLC; indicating that the proposed electroanalytical method has considerably sensitivity and precision. The results clearly indicated that, cork-graphite sensor represents a novel tool, offering a significant development over unmodified carbon materials.