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R9 Laboratory SOP 594
ANALYSIS OF NITRITE AND NITRATE IN WATER
Summary
This method is for the determination of nitrate-N + nitrite-N in drinking, surface, and saline waters, domestic and industrial waste. This SOP is based on EPA Method 353.2, Revision 2.0. The applicable range is 0.3 to 2.0 mg/L. The range can be extended for high level samples through dilution. The quantitation limit for nitrate-N + nitrite-N is 0.3 mg/L.
A filtered sample is passed through a column containing granulated copper-cadmium to reduce nitrate-N to nitrite-N. The nitrite (that originally present plus reduced nitrate) is determined by diazotizing with sulfanilamide and coupling with N-(1-naphthyl)-ethylenediamine dihydrochloride to form a highly colored azo dye which is measured colorimetrically. Separate, rather than combined nitrate-N+nitrite-N, values are readily obtained by carrying out the procedure first with, and then without, the Cu-Cd reduction step.