Hach DR/850, Procedures Manual, Page: 240 / 460

240
Estimated Detection Limit
The estimated detection limit for program 50 is 0.5 mg/L NO
3
-
-N
and 0.8 mg/L NO
3
-
-N for program 51. For more information on
the estimated detection limit, see Section 1 .
Interferences
Summary Of Method
Cadmium metal reduces nitrates present in the sample to nitrite.
The nitrite ion reacts in an acidic medium with sulfanilic acid to
form an intermediate diazonium salt which couples to gentisic
acid to form an amber-colored product.
Pollution Prevention and Waste Management
NitraVer 5 contains cadmium metal. Both samples and reagent
blanks will contain cadmium (D006) at a concentration regulated
as hazardous wastes by the Federal RCRA. Do not pour these
solutions down the drain. See
Section 3 for more information on
proper disposal of these materials.
Interfering
Substance
Interference Levels and Treatments
Chloride Chloride concentrations above 100 mg/L will cause low results.
The test may be used at high chloride concentrations
(seawater) but a calibration must be done using standards spiked to
the same chloride concentration.
Ferric iron All levels
Nitrite All levels
Compensate for nitrite interference as follows:
Add 30-g/L Bromine Water dropwise to the sample in Step 3 until a
yellow color remains.
Add one drop of 30-g/L Phenol Solution to destroy the color. Pro-
ceed with Step 4. Report the results as total nitrate
and nitrite.
pH Highly buffered samples or extreme sample pH may exceed the
buffering capacity of the reagents and require sample pretreatment.
Strong oxidizing
and reducing sub-
stances Interfere at all levels.
NITRATE, High Range,
continued