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 reactio n of propanethiol at a cobalt phthalocyanine modified screen printed c arbon electrode coated with a hydrogel. Cyclic voltammograms exhibit o ne anodic peak at + 0.45 V in the potential range from 0 to + 0.7 V. T he peak is considered to result from the electrocatalytic oxidation of propanethiol to produce the corresponding disulfide. Hydrodynamic vot ammetry revealed one well defined anodic wave, and the optimum potenti al for amperometric studies was found to be + 0.5 V. Calibration studi es were performed for devices on exposure to propanethiol at different concentrations; a linear response was obtained over the range 6-22 vp m. A method is proposed to estimate the diffusion coefficient in gels based on the amperometric data and the free boundary model of diffusio n. 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 coeffici ent 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 ge l. (C) 1997 Elsevier Science S.A.