Surfactant modified zeolite carbon paste electrode (SMZ-CPE) as a nitrate selective electrode

Abstract

A nitrate-selective electrode based on surfactant-modified zeolite (SMZ) particles into carbon paste was proposed (SMZ-CPE). The electrode was fully characterized in terms of composition, response time, ionic strength, thermal stability and usable pH range. The electrode containing 10% SMZ exhibited linear response range to nitrate species in the range of 1.00 × 10 −6 to 1.00 × 10 −3 M with a detection limit of 1.00 × 10 −6 M and a Nernstian slope of 59.4 ± 0.7 mV per decade of nitrate concentration. The response of the electrode to nitrate remains constant in the pH ranges of 3.5–9.8 and 1.7–10.5 for 1.00 × 10 −4 and 1.00 × 10 −2 M nitrate, respectively, and in presence of 1 × 10 −4 to 1 × 10 −3 M NaCl. The response of the electrode reaches to its equilibrium value within several seconds (10 s) after immersing the electrode in nitrate solution. Selectivity coefficients showed multivalent anions (such as arsenate, dichromate and sulfate) have higher interferences than monovalent anions (such as iodide, fluoride, bromide, chloride and thiocyanate). The electrode was used for determination of nitrate in an ammonium nitrate fertilizer sample, using direct potentiometry, and the satisfactory results were obtained. The electrode was also used for the potentiometric titration of nitrate. The validation of the obtained results in each case was proved by statistical “ t” and “ g” tests.