Screen-printed Potentiometric Selective Electrode Based on an Ammonium Quaternary Salt for Nitrate Detection

Abstract

In this study, a screen-printed electrode for nitrate ions was evaluated with a selective membrane based on tetradecyl ammonium nitrate as the ionophore, o-nitrophenyl octyl ether as the plasticizer, and polyvinyl chloride as the polymeric matrix. The electrodes were printed on polyethylene terephthalate sheets using a screen-printing frame with the electrode template. Then, the selective membrane was deposited by drop casting. The principal analytical parameters were determined by the method of additions recommended by IUPAC. The membrane showed a good linear response range of 5.38 × 10⁻⁶ to 1 × 10⁻² mol/L, being Nernstian according to the slope of −57.13 mV/dec (theoretical slope: −59.16 mV/dec), with a practical detection limit of 2.96 × 10⁻⁶ mol/L and a lower limit of linear response of 5.38 × 10⁻⁶ mol/L. The potentiometric selectivity coefficients for Cl⁻, Br⁻, I⁻, SO₄²⁻, and IO₃⁻ ions were determined using the mixed solutions method. The Br⁻ ion was found to be the most relevant interferent. The electrode showed a fast stable response (20 s), as well as the possibility of use in a wide pH range (3–12) without compromising the potentiometric response.