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

A new carbon-paste electrode, based on natural zeolite (c1inoptiolite) 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 x 10-8-1.0 x 10-3M) with a Nernstian slope of -28.3±1.0mV per decade (r2=0.9998). The limit of detection was 3.0x 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 mono hydrogen arsenate ion in comparison with other anions. The monohydrogen arsenateselective 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.