A voltammetric comparison of the properties of carbon paste electrodes containing glassy carbon microparticles of various sizes

This paper deals with comparison of carbon paste electrodes (CPEs) prepared from different sized microparticles of glassy carbon powder and mineral oil for their use in direct current voltammetry (DCV), differential pulse voltammetry (DPV) and cyclic voltammetry. Carbon pastes contained 250 mg of spherical microparticles of glassy carbon with a diameter of 0.4–12 μm, 10–20 μm, 20–50 μm or crystalline graphite with average diameter of particles 2 μm and mineral oil as a binding liquid. The electrochemical properties of CPEs were studied using potassium ferrocyanide in aqueous supporting electrolytes and 5-amino-6-nitroquinoline (5A6NQ) in mixed methanol–water supporting electrolytes. All tested electrochemical characteristics at these electrodes were compared with the performance of a solid glassy carbon electrode. The results show that when the size of glassy carbon spherical microparticles is increasing the CPE electrode passivates more easily by 5A6NQ, and obtained limits of detection for both potassium hexacyanoferrate and 5A6NQ for DPV and DCV are slightly higher. It was also confirmed that the use of crystalline graphite based paste in methanol–water mixed supporting electrolytes is not appropriate because of the quite high residual current and the noise. The most suitable electrode was CPE made from the smallest spherical microparticles (0.4–12 μm) of glassy carbon, which is easy to prepare and which has better electrochemical properties than other tested CPEs.