Nitrite, an intermediate in the nitrogen cycle, is formed during the decomposition of organic matter but readily oxidizes to form nitrate. These processes occur in wastewater treatment plants, water distribution systems, and natural waters. Nitrites are useful as corrosion inhibitors, preservatives, pigments, and in the manufacture of many organic preservative chemicals. Maximum Contaminant Level of 1 mg/L has been established by the USEPA for nitrite-nitrogen in drinking water.
In surface waters, nitrite may indicate partially decomposed organic matter, excessive discharge from a waste treatment facility, or industrial pollution. The measurement of nitrite is a means of monitoring corrosion inhibitor levels in cooling systems. In polluted waters its presence can indicate nitrate-reducing bacteria when anaerobic conditions exist.
The Colorimetric Method. Test kits containing CHEMets®, VACUettes®, or Vacu-vials® ampoules are based on a colorimetric chemistry in which nitrite reacts to form a pink azo dye. The intensity of the color is directly proportional to the concentration of nitrite in the sample. Nitrate will not interfere. Results are expressed as ppm (mg/L) NO2-N.
The Titrimetric Method. Test kits containing Titrets ampoules are based
on a titrimetric chemistry developed by CHEMetrics, Inc. This method is
particularly applicable to systems which contain nitrite corrosion inhibitors
in the presence of glycol. Ceric sulfate is the titrant. The method is
free from glycol interference in samples which contain up to 75% glycol.
Results are expressed as ppm (mg/L) NaNO2.