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

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