The miniSIA-1 instrument for nitrate assay (A) is identical with the one used for nitrite assay, albeit with addition of a Cd column which is 15 cm long 1.6 mm I.D. and filled with Cd/Cu granules (mesh 20-60) (B).

The colorimetric assay for nitrate is a three step method (C) based on reduction of nitrate to nitrite on a Cd column, followed  Gries reaction, whereby nitrite is converted into red azo dye monitored at 520nm. The assay protocol (D) is designed to sandwich 150 mcrL of sample withdrawn from the column between two 100 mcrL zones of reagent.

Nitrate Assay