This method is used for the determination of nitrite nitrogen in drinking, surface and saline waters, domestic and industrial wastes, plants and soils. The EPA range of this method is 0.01 to 1.00 mg/L as N. However, this method is also applicable to other ranges.
Nitrite is determined as an azo dye with an absorbance maximum at 540 nm following its diazotization with sulfanilamide and subsequent coupling with N-1-naphthylethylenediamine. This methodology is derived from Bratton and Marshall’s procedure for the colorimetric determination of sulfanilamide in blood. Shinn and Bendschneider and Robinson(4) appear to have first adopted this procedure for the determination of nitrate in fresh- and seawater, respectively. For details of reaction mechanisms and kinetics see references.(citation needed)
Turbid samples should be filtered before determination. Sample color absorbing at the analytical wavelength will interfere.
|Flow System||A181||0.01-1.00 mg/l as N|
|Astoria 2||A181||0.01-1.00 mg/l as N|
|rAPID-T||D181||0.05-2.00 mg/l as N|
Nitrite by Fluorometry
This method is used for the determination of nitrite in seawater and freshwater. The applicable range of this method is 0.05 to 5 µM NO2. However, this method is also applicable to other ranges.
Nitrite in the sample undergoes diazotization with fluorosceinamine in an acidic medium. The reaction is completed by addition of a strong base. The resulting dye is measured fluorometrically (480nm excitation and 520nm emission) and is directly proportional to nitrite concentration.
Iron, manganese, bromate and sulfite were determined to cause some interference at 100 fold excess or more.
|Flow System||A183||0.05 to 5 µM NO2|
|Astoria 2||A183||0.05 to 5 µM NO2|