LaMotte COD Plus Colorimeter 1922-EX2 - Manual (Page 128)

PROCEDURE
A. PREPARATION OF DILUTE ZINC INDICATOR SOLUTION
1.
Use a pipet (0352) to measure exactly 5.0 mL of *Zinc Indicator Solution
(6314) into 10 mL graduated cylinder (0416). The bottom of the curved
surface (the meniscus) of liquid should be at 5.0 mL mark. Pour this into
the bottle labeled “Dilute Zinc Indicator Solution”.
2. Use unrinsed graduated cylinder to add 10.0 mL and then 7.8 mL (total of
17.8 mL) of *Methyl Alcohol (6319) to bottle labeled “Dilute Zinc
Indicator Solution”. Cap and mix ingredients in this bottle. Do not leave
this bottle uncapped.
B. DETERMINATION OF ZINC
1. Press and hold ON button until colorimeter turns on.
2. Press ENTER to start.
3. Press ENTER to select TESTING MENU.
4. Select ALL TESTS (or another sequence containing 29 Zinc-LR) from
TESTING MENU
.
5. Scroll to and select 29 Zinc-LR from menu.
6. Rinse a clean tube (0290) with sample water. Fill to the 10 mL line with
sample.
7. Insert tube into chamber, close lid and select SCAN BLANK. (See Note)
8. Remove tube from colorimeter. Use 0.1 g spoon (0699) to add one
measure of Sodium Ascorbate Powder (6316). Use 0.5 g spoon (0698) to
add one measure of *Zinc Buffer Powder (6315). Cap and shake vigorously
for 1 minute. Some undissolved buffer may remain in the bottom of the
tube.
9. Add 3 drops of *Sodium Cyanide, 10% (6565). Cap and mix.
10. Use the 1 mL pipet assembly to add 1 mL of “Dilute Zinc Indicator
Solution”. Cap and mix.
11. Use a second plain pipet (0352) to add 4 drops of *Formaldehyde
Solution, 37% (5128). Cap and mix by inverting 15 times.
12. Insert tube into chamber, close lid and select SCAN SAMPLE. Record
result.
13. Press
OFF button to turn colorimeter off or press EXIT button to exit to a
previous menu or make another menu selection.
NOTE: For best possible results, a reagent blank should be determined to
account for any contribution to the test result by the reagent system. To
determine the reagent blank, follow the above test procedure to scan a distilled
or deionized water blank. Then follow the above procedure to perform the test
on a distilled or deionized water sample. This test result is the reagent blank.
Subtract the reagent blank from all subsequent test results of unknown samples.
It is necessary to determine the reagent blank only when a new lot number of
reagents are obtained.
COD PLUS TEST PROCEDURES 6/02 ZINC - LOW RANGE 3/3