Hach DR/850 - Page 261

261
Accuracy Check
Standard Additions Method
a) Fill three 25-mL mixing cylinders with 20 mL of sample.
b) Use the TenSette Pipet to add 0.1, 0.2, and 0.3 mL of
Ammonium Nitrogen Standard, 10 mg/L as NH
3
-N to the
three samples. Stopper the cylinders and mix well.
c) Analyze a 10-mL portion of sample as described above.
The ammonia nitrogen concentration should increase 0.05
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
Prepare a 0.40 mg/L ammonia nitrogen standard by diluting 4.00
mL of the Ammonia Nitrogen Standard Solution, 10 mg/L, to 100
mL with deionized water. Or, using the TenSette Pipet, prepare a
0.40 mg/L ammonia nitrogen standard by diluting 0.8 mL of a
Ammonia Nitrogen Voluette Standard Solution, 50 mg/L as NH
3
-
N, to 100 mL with
deionized water.
Method Performance
Precision
In a single laboratory using a standard solution of 0.40 mg/L
ammonia nitrogen (NH
3
-N) and two representative lots of reagent
with the instrument, a single operator obtained a standard
deviation of +
0.02 mg/L ammonia nitrogen.
Estimated Detection Limit
The estimated detection limit for program 64 is 0.02 mg/L NH
3
-
N. For more information on the estimated detection limit, see
Section 1.
NITROGEN, AMMONIA, continued