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NITROGEN, AMMONIA, Low Range, Test 'N Tube,
Method Performance
Interferences
Interfering Substance
Calcium
Iron
Magnesium
Nitrite
Nitrate
Orthophosphate
pH
Sulfate
c) Analyze each sample as described above. The nitrogen
concentration should increase 0.20 mg/L for each 0.1 mL
of standard added.
d) If these increases do not occur, see Standard Additions,
Section 1, for more information.
Standard Solution Method
To check accuracy, use a 1.0 mg/L Nitrogen, Ammonia Standard
Solution listed under Optional Reagents. Or, dilute 1 mL of
solution from a
50 mg/L Ampule Standard for Nitrogen, Ammonia to 50 mL with
deionized water using a 50-mL volumetric flask.
Precision
In a single laboratory, using a standard solution of 1.0 mg/L
ammonia nitrogen and two representative lots of reagent with the
instrument, a single operator obtained a standard deviation of
+0.02 mg/L NH
-N.
3
Estimated Detection Limit
The estimated detection limit for program 66 is 0.08 mg/L NH
N. For more information on the estimated detection limit, see
Section 1.
Interference Level and Treatment
2500 mg/L as CaCO
3
1. Determine the amount of iron present in the sample following one of the total
iron procedures.
2. Add the same iron concentration to the deionized water in step 4. The
interference will then be successfully blanked out.
5000 mg/L as CaCO
3
-
30 mg/L as NO
-N
2
-
250 mg/L as NO
-N
3
3-
250 mg/L as PO
-P
4
Acidic or basic samples should be adjusted to about pH 7. Use 1 N Sodium
Hydroxide Standard Solution for acidic samples and 1 N Hydrochloric Acid
Standard Solution for basic samples.
2-
300 mg/L as SO
4
267
continued
-
3
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