Hach DR2400 - Page 140

Chloramine (Mono)
Chloramine (Mono)
Page 4 of 6
Chloramine (Mono)_MP_Low_MCF_Eng_2400.fm
Accuracy Check
To check test accuracy, prepare the following 4.5-mg/L (as Cl
2
) monochloramine
standard fresh before use.
1. Add the contents of one Buffer Powder Pillow, pH 8.3, to about 50-mL of
organic-free water in a clean 100-mL Class A volumetric flask. Swirl to
dissolve the powder.
2. Using a Class A volumetric pipet, transfer 2.00 mL of Nitrogen, Ammonia
Standard Solution, 100-mg/L as NH
3
–N into the flask.
3. Dilute to volume with organic-free water, cap, and mix thoroughly. This is a
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 stir bar.
5. Obtain a recent lot of Chlorine Solution Ampules, 50–70 mg/L, and note the
actual free chlorine concentration for this lot.
6. Calculate the amount of Chlorine Solution to be added to the ammonia
standard using the following equation:
7. Open an ampule and, using a glass Mohr pipet, add the calculated amount of
Chlorine Solution slowly to the ammonia standard, while mixing at medium
speed on a stir-plate.
8. Allow the monochloramine solution to mix for 1 minute after all Chlorine
Solution is added.
9. Quantitatively transfer the monochloramine solution to a clean 100-mL
Class A volumetric flask. Dilute to the mark with organic-free water, cap, and
mix thoroughly. This is a nominal 4.5-mg/L (as Cl
2
) monochloramine
standard.
10. Use this standard within 1 hour of preparation. Analyze according to the
High Range Monochloramine procedure described above.
11. To adjust the calibration curve using the reading obtained with the 4.5-mg/L
standard solution, touch
Options on the current program menu. Touch
Standard Adjust.
12. Touch
On. Touch Adjust to accept the displayed concentration (the value
depends on the selected chemical form). If an alternate concentration is used,
touch the number in the box to enter the actual concentration, then touch
OK.
Touch
Adjust.
Method Performance
Precision
Standard: 2.52 mg/L Cl
2
See Section 3.4.3 Precision on page 42 for more information, or if the standard
concentration did not fall within the specified range.
mL chlorine solution required
455
free chlorine concentration
----------------------------------------------------------------------=
Program 95% Confidence Limits of Distribution
66 2.41–2.63 mg/L Cl
2