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Tubular potentiometric detector used to determine As(V) in sediment extracts by flow injection

The construction and evaluation of a tubular potentiometric detector sensitive to As(V) ions is described. This electrode, with no inner reference solution, is comprised of a FeOOH–SiO2–graphite composite agglutinated with an epoxy resin. For As(V) ion concentrations in the range 1.0 × 10−5 to 1.0 × 10−1 mol L−1, the sensor is used as the selective electrode in an FIA system along with a commercial Ag/AgCl reference electrode. In optimal conditions, the practical limit of detection is 4 × 10−6 mol L−1 and a sampling rate of 40 h−1 can be achieved. The system was applied to estimate As(V) levels in sediments of a drinking water distributor in Zimapán (Mexico), an area known to be polluted with this element. The As(V) concentrations detected in the different extracts of sediments generated by the sequential modified BCR three-step extraction procedure (BCR-SEP) were comparable to those obtained by electrothermal atomic absorption spectroscopy (ET-AAS).