Abstract: Near thirty years have passed since the first attempt to develop a selective electrode for phosphate and no substantial progress has been made because all reported electrodes have poor selectivity, reproducibility or short lifetime.In this report, we describe a phosphate ion sensitive electrode based on cobalt, which is easily available for practical application in determination of phosphate concentration.The detection limit of 8×10^-6mol/Land a linear range of response from 1×10^-5mol/L to 1×10^-2mol/L for dihydrogen phosphate activity with a slope of 56mV/dec.are obtained in pH 4.0 buffer solutions.The electrode has an excellent selectivity for the dihydrogen phosphate with respect to many common anions such as sulfale,chloride,nitrate and acetate.The electrode shows a long term stability and reproducibility of response for the dihydrogen phosphate.

Key words: Phosphate, Ion selective electrode, Dihydrogen phosphate