Hach DR/850 Procedures Manual page 94

CHLORAMINE, MONO, High Range, continued
9.
After the timer
beeps, wipe the prepared
vial and place it into the
instrument. Cover the
sample vial tightly with
the instrument cap.
Sampling and Storage
Accuracy Check
10.
Press:
READ.
The cursor will move to
the right , then the
results in mg/L
monochloramine (as
Cl ) will be displayed.
2
Analyze samples for monochloramine immediately after
collection. Rinse the sample container several times with the
sample water allowing it to overflow each time. If sampling from
a tap, let the water flow for at least 5 minutes. Cap the container
so that there is no head space (air) above the sample.
Prepare the following monochloramine standard fresh before use:
1. Using a clean 100-mL Class A volumetric flask, add the
contents of one Buffer Powder Pillow, pH 8.3, to
approximately 50 mL of organic-free water. Swirl to dissolve
the powder.
2. Use a Class A volumetric pipet to transfer 2.00 mL of
Nitrogen Ammonia Standard Solution, 100-mg/L as NH
into a flask.
3. Dilute to volume with organic-free water. Cap and mix
thoroughly. This is the 2.00-mg/L buffered ammonia
standard.
4. Pipet 50.00 mL of the buffered ammonia standard into a
clean 100-mL beaker. Add a magnetic stir bar and place the
beaker on a stir plate.
5. Note the free chlorine concentration for the Chlorine Solution
Ampules, 50–70 mg/L. Use ampules from a recent lot.
94
–N,
3