Development of a carbon composite electrode made from polyethylene and graphite powder modified with copper(I) oxide

Solid carbon composite electrodes (CCEs) prepared by copper(I) oxide (Cu2O) dispersed in polyethylene and graphite powder have been investigated for use as working electrode in amperometric flow-through detection in alkaline solutions. The effects of matrix composition, electrocatalyst loading, short- and long-term electrode stability, noise current, and sensitivity were assessed using d-mannitol as a model compound. Excellent sensitivity accompanied by a low residual current was observed with a 50% (w/w) Cu2O loading level in the carbon paste matrix. An estimate value of the double layer capacitance, evaluated by cyclic voltametry in 0.48 M NaOH, was about 1360 μF/mm2. Upon optimizing the sensing electrode in terms of composite electrode formulation, hydroxide ion concentration, and operating potential, the detection limit for d-mannitol in flow injection mode, using a wall-jet flow cell, was 5 μM for 50 μl injections. The bulk Cu2O-CCEs exhibit good mechanical stability under forced flow hydrodynamic conditions, and overall offers the advantage of a very low background current. An additional inherent feature of these catalyst-modified electrodes is their renewal capability; the surface can rapidly be renewed by a simple polishing procedure making the amperometric sensor very attractive for routine quantitative measurements.