Development of a sensitive nitrate-selective electrode for on-site use in fresh waters

Abstract

Twenty seven membranes hot pressed from mixtures of a variety of quaternary ammonium salt sensor molecules and mediators in Krynac polymer have been evaluated as nitrate-selective electrode membranes suitable for use in fresh waters. The best performance was obtained from a covalently bound triallyldecylammonium nitrate sensor having a Nernstian slope of –57.7 mV decade^–1 over a nitrate range of 1 × 10^–1 to 1.2 × 10^–5 mol dm^–3 NO₃^– with a limit of detection of 8.8 × 10^–6 mol dm^–3 NO₃^–.Membrane performance remained unchanged for at least six months use. Interfering ions, temperature and pH dependency studies are reported . Selectivity towards chloride at the 10^–2 mol dm^–3 level was measured as k^pot_{NO3^–,Cl^–} 1 × 10^–4.