Nitrate
Nitrate
Page 4 of 6
Nitrate_AVPP_Mid_CDR_Eng_Ody.fm
Interferences
Sample Collection, Storage and Preservation
Most reliable results are obtained when samples are analyzed as soon as possible
after collection. If prompt analysis is impossible, store samples in clean plastic or
glass bottles for up to 24 hours at 4 °C. To preserve samples for longer periods,
add 2 mL of Concentrated Sulfuric Acid (H
2
SO
4
) (Cat. No. 979-49) per liter and
store at 4 °C.
9. Within two minutes
after the timer beeps,
wipe the ampule and
place it into the cell
holder.
10. Touch Read.
Results will appear in
mg/L NO
3
–
–N.
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 Interferes at all levels
Nitrite
Interferes at all levels
Compensate for nitrite interference as follows:
a) Add 30-g/L Bromine Water (Cat. No. 2211-20) dropwise to the sample in step 3 until a yellow color remains.
b) Add one drop of 30-g/L Phenol Solution (Cat. No. 2112-20) to destroy the color.
Proceed 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
substances
Interfere at all levels
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