From the LaMotte Colorimeter 1200
TEST METHOD SPECIFICATIONS
This method determines nitrate levels in drinking, surface, saline waters, domestic, and
0 - 3.0 ppm
Nitrate Nitrogen (Range can be extended by dilution.)
Powdered cadmium is used to reduce nitrate to nitrite. The nitrite that is originally
present plus reduced nitrate is determined by diazotization of sulfanilamide and nitrite
followed by coupling with N-(1 naphthyl) -ethylenediamine dihydrochloride to form a
highly colored azo dye which is measured colorimetrically.
Nitrite interferences at all levels. Use the following equation to compensate for nitrite
interferences: Test result (ppm) - (Nitrite-N (ppm) x 5.5) = true Nitrate-N reading.
Strong oxidizing and reducing substances interfere. Low results might be obtained for
samples that contain high concentrations of iron and copper.