Electrocatalytic, diffusional and analytical characteristics of a cobalt phthalocyanine modified, screen-printed, amperometric gas sensor for propanethiol

Cyclic voltammetry was used to investigate the electrochemical reaction of propanethiol at a cobalt phthalocyanine modified screen printed carbon electrode coated with a hydrogel. Cyclic voltammograms exhibit one anodic peak at + 0.45 V in the potential range from 0 to + 0.7 V. The peak is considered to result from the electrocatalytic oxidation of propanethiol to produce the corresponding disulfide. Hydrodynamic votammetry revealed one well defined anodic wave, and the optimum potential for amperometric studies was found to be + 0.5 V. Calibration studies were performed for devices on exposure to propanethiol at different concentrations; a linear response was obtained over the range 6-22 vpm. A method is proposed to estimate the diffusion coefficient in gels based on the amperometric data and the free boundary model of diffusion. The diffusion coefficient of propanethiol in agarose gel was found to be approximate to 1.96 x 10(-5) cm(2) s(-1). The diffusion coefficient obtained at a gel free sensor was calculated to be approximate to 2.5 x 10(-5) cm(2) s(-1). The lower value obtained for the former may be due to obstruction by the polymer particles which constitute the gel. (C) 1997 Elsevier Science S.A.