247
Estimated Detection Limit
The estimated detection limit for program 55 is 0.01 mg/L NO
3
-
-
N. 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
chromotropic acid to form a pink-colored product.
Pollution Prevention and Waste Management
NitaVer 6 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
Calcium 100 mg/L
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: This method measures both the nitrate and nitrite in
the sample. If nitrite is present, the nitrite nitrogen test Program
60 should be done on the sample. Pretreat the nitrate nitrogen
sample with the following pretreatment. Then subtract the
amount of nitrite found from the results of the LR nitrate
nitrogen test using the pretreated sample.
1. Add 30-g/L Bromine Water dropwise to the sample in Step 3
until a yellow color remains. Mix after each drop.
2. Add one drop of 30-g/L Phenol Solution to destroy the yellow
color.
3. Proceed with the LR Nitrate procedure.
pH Highly buffered samples or extreme sample pH may exceed the
buffering capacity of the reagents and require sample
pretreatment.
Strong oxidizing and
reducing
substances
Interfere at all levels
NITRATE, Low Range, continued
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