Due to the absence of operational requirements and its unidentified solutions ,this
study presented definition alternative analytical and technical conditions for the
continuation of nitrate-selective electrode working. Many electrolytes were teste
d
(ammonium sulfate, ammonium acetate and ammonium chloride). The technical and
analytical conditions shows that the best response which give the Nernst slope of the
electrode had been obtained by adding 0.5ml of ammonium sulfate (3mol / l), and the
response time was 20sec, by the time that values stabilized for 15sec. The study of pH
effect on the electrode response also showed that electrode works within the range (2-8) of
pH and that the best response was at pH = 5.5 by using acetic acid-sodium acetate buffer.
The effect of temperature on the potential electrode was studied ,it showed that the Nernest
electrode response realized within the range (18-37) C0of temperature.While Studying the
effect of some interfering ions such as (OH-, HCO3
-, CO3
2-,Cl-,NO2
-) on the work of the
electrode showed low values of the coefficient of selectivity, which did not exceed 3×10-2
that the electrode was not affected by the presence of these ions. The chosen conditions
were experimented on standard solutions, which showed that the electrode is working
within the range (10-4-10-1) mol / l of concentrations. When the concentrations was about
10-5mol/l or less than that, it was necessary to soak the electrode in solution which has low
concentration for at least one hour, and diluted the taken volumes ten times . These
technical and analytical conditions was applied on standard solutions and environmental
samples(water), which showed the accuracy ,correctly and authenticity of the
measurements.
