Hach DR/850 Procedures Manual page 266

NITROGEN, AMMONIA, Low Range, Test 'N Tube,
9.
Wipe the outside of
the vials with a towel.
After the timer beeps,
place the blank into the
adapter. Tightly cover
the vial with the
instrument cap.
Note: Wipe with a damp
cloth followed by a dry one
to remove fingerprints and
other marks.
Sampling and Storage
Accuracy Check
10.
Press:
ZERO
The cursor will move to
the right, then the
display will show:
0.00 mg/L NH3-N
Collect samples in clean plastic or glass bottles. Best results are
obtained with immediate analysis. If chlorine is known to be
present, add one drop of 0.1 N sodium thiosulfate for each 0.3
mg/L Cl in a one liter sample. Preserve the sample by reducing
2
the pH to 2 or less with hydrochloric acid (at least 2 mL). Store at
° °
4 C (39 F) or less. Preserved samples may be stored up to 28
days. Before analysis, warm samples to room temperature and
neutralize with 5.0 N sodium hydroxide. Correct the test result for
volume additions. See Correcting for Volume Additions on page
22 for more information.
Standard Additions Method
a) Snap the neck off a Nitrogen, Ammonia Ampule Standard
Solution, 50 mg/L NH
b) Use the TenSette Pipet to add 0.1, 0.2, and 0.3 mL of
standard to three 25 mL samples. Mix thoroughly.
11.
Place the prepared
sample in the adapter.
Push straight down on
the top of the vial until
it seats solidly into the
adapter.
Note: Do not move the vial
from side to side as this can
cause errors.
-N.
3
266
continued
12.
Tightly cover the
sample cell with the
instrument cap.
Press:
READ
The cursor will move to
the right, then the result
in mg/L ammonia
nitrogen will be
displayed.
Note: Standard Adjust may
be performed using a
prepared standard (see
Standard Adjust (Adjusting
the Standard Curve) on
page 47).