Abstract
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.
Highlights
The pH control of aqueous solutions is an important requirement in routine laboratories, industrial processes, alcoholic fermentation, and in medical and agricultural sciences
The application of Ta2O5, ZrO2, Al2O3 and Si3N4 films produced on SiO2-Si substrates (CHEMFETS) as pH-sensitive membranes in flow injection analysis (FIA) has been described in Teixeira et al
The potentiometric response of the Fe2O3-based graphite-epoxy tubular electrode in aqueous solutions of different pH is determined by a charge transfer reaction at the Fe2O3/ aqueous solution interface
Summary
The pH control of aqueous solutions is an important requirement in routine laboratories, industrial processes, alcoholic fermentation, and in medical and agricultural sciences. The results of a systematic evaluation of a Fe2O3-based graphite-epoxy tubular electrode as pH sensor in flow injection potentiometry are reported. The effect of electrode composition and the response characteristics under different flow injection conditions (flow rate and injection sample volume) on the Fe2O3based graphite-epoxy tubular electrode were investigated.
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