Potentiometric determination of monohydrogen arsenate by zeolite-modified carbon-paste electrode

A new carbon-paste electrode, based on natural zeolite (clinoptiolite) modified by the Fe2 + ion as carrier, was developed. The electrode exhibits a linear response to monohydrogen arsenate over a wide concentration range (5.0 × 10−8–1.0 × 10−3 M) with a Nernstian slope of −28.3 ± 1.0 mV per decade (r 2 = 0.9998). The limit of detection was 3.0 × 10−8 M. It has a fast response time 5–10 s and can be used for more than 2 months. Selectivity coefficients determined by the fixed interference method indicate that a good discriminating ability towards monohydrogen arsenate ion in comparison with other anions. The monohydrogen arsenate-selective electrode could be used in the pH range of 7.0–11.0. This chemically modified carbon-paste electrode was successfully used for the determination of arsenic in water and wastewater samples.