1.1 Methods
Notes:
1. Strong alkaline or acidic water samples must be adjusted to approx. pH 7 before analysis
(use 1 mol/l Hydrochloric acid resp. 1 mol/l Sodium hydroxide).
2. If chlorine is known to be present, add one drop of 0.1 mol/l Sodium thiosulfate for
each 0.3 mg/l Cl
2
in a one litre water sample.
3. Iron interferes with the test. The interferences will be eliminated as follows:
Determine the amount of total iron present in the water sample. To produce the blank
add an iron standard solution with the same iron concentration to the vial (point 1)
instead of deionised water
4. Conversion:
mg/l NH
4
= mg/l N x 1.29
mg/l NH
3
= mg/l N x 1.22
5.
N
NH
4
NH
3
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