LaMotte SMART Spectro Spectrophotometer - Manual (Page 193)

APPLICATION: Drinking, surface, and saline waters; domestic and
industrial waters.
RANGE: 0.00–3.00 ppm Nitrate Nitrogen
MDL: 0.02 ppm
METHOD: 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.
SAMPLE HANDLING
& PRESERVATION:
Analysis should be made as soon as possible. If
analysis cannot be made within 24 hours, the sample
should be preserved by refrigeration at 4°C. When
samples must be stored for more than 24 hours, they
can be preserved by adding 2 mL of concentrated
sulfuric acid per liter of sample. For best results,
the analysis for nitrate should be determined at
temperatures between 20°C and 25°C.
INTERFERENCES: Nitrite interferes at all levels. Strong oxidizing and
reducing substances interfere. Low results might be
obtained for samples that contain high concentrations of
iron and copper.
NITRATE-NITROGEN, Low Range SMART Spectro Test Procedures 2.11
Test P
rocedures