The general principle employed by the FIA methodology is the
reduction of nitrate to nitrite using a copperised cadmium
(Cu-Cd) reduction column. The resultant stream of nitrite which
is stabilized by a buffer at a pH of 8.5 is colorimetrically determined
with Griess reagent (mixture of SA and NED). This furnishes
the total nitrate and nitrite content of the sample. To quantify only
nitrite, the sample is not allowed to pass through the Cu-Cd reduction
column. Thus the exclusion of the nitrite values from the total
resulted in superlative nitrate quantification in a sample.
The quantification parameters and the figure of merits of the
analytical method are listed in Table 2. All pH measurements were