Hach DR/700 Procedures Manual page 283

NITRATE, HR,
a) Add Bromine Water, 30 g/L, drop-wise to the sample in Step 4 until a
yellow color remains.
b) Add one drop of Phenol Solution, 30 g/L, to destroy the color.
c) Proceed with Step 4. Report results as total nitrate and nitrite.
Strong oxidizing and reducing substances will interfere. Ferric iron
causes high results and must be absent. Chloride concentrations above
100 mg/L will cause low results. The test may be used at high chloride
levels (i.e., seawater), but a calibration must be performed using
standards spiked to the same chloride concentration. See Calibrations
paragraph 3.2.4 in the DR/700 Instrument Manual for more information.
Highly buffered samples or extreme sample pH may exceed the
buffering capacity of the reagents and require sample pretreatment; see
Interferences, pH (Section I).
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. This salt couples to gentisic acid to form
an amber-colored product.
Nitrate can be determined directly using the Nitrate Ion Selective
Electrode (Cat. No. 44560-71).
REQUIRED REAGENTS (Using Powder Pillows)
Description
NitraVer 5 Nitrate Reagent
Powder Pillows, 10 mL size . 1 pillow . . . . 100/pkg . . . . . . . . 21061-69
REQUIRED REAGENTS (Using AccuVac Ampuls)
NitraVer 5 Nitrate Reagent
AccuVac Ampul . . . . . . . . . 1 ampul . . . . 25/pkg . . . . . . . . 25110-25
REQUIRED APPARATUS (Using Powder Pillows)
Clippers, for opening
powder pillows . . . . . . . . . . 1 . . . . . . . . . each . . . . . . . . . . . 968-00
continued
Quantity
Per Test
50-33
Unit Cat. No.