Journal of the Brazilian Chemical Society
On-line version ISSN 1678-4790
TEIXEIRA, Marcos F. de S. et al. Evaluation of a Fe2O3-based graphite-epoxy tubular electrode as pH sensor in flow injection potentiometry. J. Braz. Chem. Soc. [online]. 2000, vol.11, n.1, pp. 27-31. ISSN 1678-4790. http://dx.doi.org/10.1590/S0103-50532000000100006.
A systematic evaluation of a Fe2O3 graphite-epoxy tubular electrode was investigated through pH measurements in a single-channel flow injection system. The tubular electrode was obtained by deposition of a mixture of iron(III) oxide, graphite powder and epoxy resin into a hole previously made in the injection channel (of a polyuretane resin block). The effect of electrode composition and flow injection parameters (flow rate and injection sample volume) on the Fe2O3-tubular-electrode response was initially evaluated in quintuplicate (confidence level of 95%). The best potentiometric response (E/mV = 178.2 - 26.5 pH; r = 0.9995) was reached in the pH range 2 to 12 with an electrode composition in mass of 30% Fe2O3, 20% graphite and 50% epoxy resin, injection sample volume of 300 mL and a flow rate of 3.2 mL min-1. The frequency rate was 90 h-1 and a useful lifetime of at least six months (more than 2000 determinations) was obtained.
Keywords : Fe2O3 tubular electrode; graphite-epoxy; pH sensor; flow injection analysis.