Development of New coated wire nitrate selective electrode sensor for determination of nitrate concentration in an aqueous sample

A coated wire nitrate selective electrode has been prepared and characterized. The electrochemical cell for potentiometric measurement consist of a miniaturized homemade Ag/AgCl reference electrode and a coated wire nitrate selective electrode (CWISE) immersed in nitrate solution to be studied, and mV-meter. Standard potential of the Ag/AgCl reference electrode was 0.2496 V. Preparation of CWISE was realized by covering platinum wire of 0.4 mm diameter with thin polymeric membrane. The membrane solution has been prepared by mixing of 0.25 g of polyvinil chloride (PVC) as supporting material, 0.7 g of Aliquat 336-nitrate as ionophore and 5.8 g of dioctylphtalate (DOP) as plasticizer in 10 mL of tetrahydrofuran (THF). The CWISE for nitrate measurement showed non-nerstienne sensitivity at the range 10-1 to 10-4 M of principal ion. The selectivity of CWISE has been studied by determination of its potentiometric selectivity coefficient. The results of these determinations was K^Pot_NO3-.I >; K^Pot_NO3-,NO3- >; K^Pot_NO3-,Cl- >; K^Pot_{NO3-, SO4}=. For quantitative analysis by potentiometric method, the calibration curve should be updated.