Hach DR/850, Руководство по процедурам, Страница: 252 / 460

252
Sampling and Storage
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.
Accuracy Check
Standard Solution Method
Pipet 5.00 mL of a fresh 250 mg/L NO
2
-
-N standard into a 250.0
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
2
- -N standard solution, dilute 10.00 mL of the
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
2
- -N standard in place of the
sample. Results should be between 0.090 and 0.110 mg/L
NO
2
- -N.
Method Performance
Precision
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
2
- -N for the powder pillow method and ±0.003
mg/L NO
2
- -N for the
AccuVac method.
9.
Place the AccuVac
Ampul into the cell
holder. Tightly cover the
ampul with the
instrument cap.
10.
Press:
READ
The cursor will move to
the right, then the result
in mg/L nitrite nitrogen
will be displayed.
NITRITE, Low Range,
continued