LaMotte SMART 2 - Manual (Page 131)

PROCEDURE
Use COD adapter (see p. 22).
1. Homogenize sample if necessary.
2. Preheat COD heater block to 150±2°C.
3. Remove cap from COD tube. Hold tube at a 45° angle. Use a graduated
pipet, to carefully add 0.2 mL sample water allowing the sample to run
down the side of the tube.
4. Cap and mix thoroughly.
5. Rinse the outside of the tube with distilled water. Wipe dry with a paper
towel.
6. Repeat steps 3 through 5 using 0.2 mL distilled water. This is the reagent
blank.
7. Place tubes in preheated COD block heater and maintain temperature at
150±2°C for two hours.
8. At the end of the heating period turn the heater off. Wait 20 minutes for
the tubes to cool to 120°C or less.
9. Remove tubes from block heater. Invert several times to mix.
10. Allow to cool to room temperature.
11. Press and hold ON button until colorimeter turns on.
12. Press ENTER to start.
13. Press ENTER to select TESTING MENU.
14. Select ALL TESTS (or another sequence containing 27 COD HR) from
PROGRAMMED TESTS
menu.
15. Wipe the blank tube with a damp towel to remove fingerprints and
smudges. Wipe with a dry towel.
16. Scroll to and select 27 COD HR from menu.
17. Insert reagent blank tube into chamber. Select SCAN BLANK.
18. Remove tube from colorimeter.
19. Insert digested water sample tube into chamber. Select SCAN SAMPLE.
Record result. For the most accurate results, take three readings on each
sample and average the results.
20. Press
OFF
button to turn colorimeter off or press
EXIT
button to exit to
a previous menu or make another menu selection.
þ NOTES: Reagents are light sensitive. Unused reagents should be stored in the
shipping container, and in the refrigerator if possible, until needed.
A reagent blank should be run with each set of samples and with each lot of
reagents.
The reacted blank will be stable if stored in the dark.
To eliminate error caused by contamination, wash all glassware with 20%
sulfuric acid.
For greater accuracy, a minimum of three repetitions should be performed and
the results averaged.
Smart2 TEST PROCEDURES 03.05 COD–HR 3/3