Hach DR/850 Procedures Manual page 279

NITROGEN, TOTAL INORGANIC, Test 'N Tube,
17.
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.
Sampling And Storage
Accuracy Check
18.
Tightly cover the
sample cell with the
instrument cap.
Collect samples in clean plastic or glass bottles. Best results are
obtained with immediate analysis.
If chlorine is known to be present, add 1 drop of 0.1 N sodium
thiosulfate for each 0.3 mg/L Cl
Preserve the sample by reducing the pH to 2 or less with
concentrated hydrochloric acid (at least 2 mL). Store at 4 °C (39 °F)
or less. Preserved samples may be stored up to 28 days. Warm
samples to room temperature and neutralize with 5 N Sodium
Hydroxide before analysis. Correct the test result for volume
additions; see Correcting for Volume Additions in Section 1.
Standard Additions Method
a) Fill three 25-mL graduated mixing cylinders with 25 mL of
sample.
b) Snap the neck off a fresh High Range Nitrate Nitrogen
PourRite Ampule Standard, 500 mg/L NO
c) Use the TenSette Pipet to add 0.1, 0.2, and 0.3 mL of
standard, respectively, to 3 25-mL mixing cylinders. Mix
thoroughly.
19.
Press:
READ
The cursor will move to
the right, then the result
in mg/L total inorganic
nitrogen will be
displayed.
Note: Standard Adjust may
be performed using a
prepared standard (see
Section 1).
in a 1 liter sample.
2
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continued
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3