Hach DR/850 Procedures Manual page 252

Colorimeter
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NITRITE, Low Range,
9.
Place the AccuVac
Ampul into the cell
holder. Tightly cover the
ampul with the
instrument cap.
Sampling and Storage
Accuracy Check
Standard Solution Method
Method Performance
Precision
continued
10.
Press:
READ
The cursor will move to
the right, then the result
in mg/L nitrite nitrogen
will be displayed.
Collect samples in clean plastic or glass bottles.
Store at 4 °C (39 °F) or lower and analyze within 48 hours. Warm
to room temperature before running the test.
Do not use acid preservatives.
Remove the suspended solids by filtration.
Pipet 5.00 mL of a fresh 250 mg/L NO
mL volumetric flask. Dilute to the mark with deionized water.
This makes a 5.00-mg/L intermediate standard. To prepare a
0.100-mg/L NO
5.00-mg/L intermediate standard to 500 mL in a volumetric flask.
Prepare this solution immediately before use.
Run the test using the 0.100 mg/L NO
sample. Results should be between 0.090 and 0.110 mg/L
-
NO
-N.
2
In a single laboratory, using a standard solution of 0.250 mg/L
nitrite nitrogen and two representative lots of reagent with the
instrument, a single operator obtained a standard deviation of
±0.001 mg/L NO
mg/L NO
-
-N for the
2
AccuVac method.
-
-N standard solution, dilute 10.00 mL of the
2
-
-N for the powder pillow method and ±0.003
2
252
-
-N standard into a 250.0
2
-
-N standard in place of the
2

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