The nitrite ion (NO2-) is commonly determined by a colormetric procedure using a reaction called the Griess reaction. Im this reaction the sample containing nitrate is reacted with sulfanilimide and N-(1-napthyl)ethylenediamide to form a colored species that absorbs at 550 nm, By using an automated flow aalysis instrument, the followig results were obtained for standard solutions of nitrate and for a sampke containing an unknown amount of nitrite.
Solution Absorbance at 550 nm
Blank 0.002
2.00 ?M 0.065
6.00 ?M 0.205
10.00 ?M 0.388
14.00 ?M 0.474
18.00 ?M 0.598
Unknown 0.402