A Spectrophotometric Method for the Determination of Nitrite and Nitrate

Abstract

A simple, rapid spectrophotometric method for the determination of nitrite and nitrate in water, soil
and pharmaceutical preparation samples has been developed. Determination of nitrite is based on the
reactions involving sulfanilic acid with methyl anthranilate as the coupling agents and determination
of nitrate is based on their reduction to nitrite in the presence of Zn/NaCl. The produced nitrite is
subsequently diazotized with sulfanilic acid then coupled with methyl anthranilate to form an azo dye
which is measured at 493 nm. The method is optimized for acidity, amount of reagents required and
tolerance amount of other ions. The range of linearity for sulfanilic acid-methyl anthranilate couple
was found to be 0.2-8.0 µg/mL of nitrite with molar absorptivity be 1.03x104
Lmol-1cm-1 and sandell’
s
sensitivity 4.5x10-3 µg cm-2 . The detection limit and quantitation limit of the nitrite determination are
found to be 0.93 µgmL−1 and 2.82 µgmL−1 respectively. This method has been successfully applied to
the determination of trace amounts of nitrite and nitrate in water, soil and pharmaceutical preparations