A new nitrate-selective liquid-membrane electrode based on the tris(2,2',2 " -salicylideneimino)triethylamine-iron(III) complex has been developed. This electrode exhibits a linear Nernstian response over the range 10(-1) - 10(-4) M of nitrate, with a slope of 54.3 +/- 0.9 mV per p[NO3]. The effects of the pH and the liquid-membrane composition were also investigated. ne lifetime of the electrode is at least one month. The selectivity coefficients for ten monovalent ions were calculated. The preparation procedure of the electrode is very easy and inexpensive. Moreover, the proposed electrode was applied for the determination of nitrate in fertilizers.