LaMotte smart spectro 2 Operator's Manual page 139

HEXAVALENT CHROMIUM PROCEDURE
Use universal sample holder.
1. Press ON button to turn spectrophotometer on.
2. Scroll to and select 22 Chromium from menu.
3. Scroll to and select ALL TESTS (or another sequence containing
22 Chromium) from TESTING MENU.
4. Scroll to and select 22 Chromium from menu.
5. Rinse a clean tube (0290) with sample water. Fill to 10 mL line with sample water.
6. Insert tube into chamber, close lid and select SCAN BLANK.
7. Remove tube from Spectro. Use 0.1 g spoon (0699) to add one level measure
of *Chromium Reagent Powder (V-6276). Cap and shake for one minute. Wait 3
minutes.
8. During the waiting period, fold a piece of fi lter paper in half, then in half again to form a
cone. Push corners together to open end, and insert into funnel (0459).
9. At the end of 3 minute waiting period, fi lter sample into a clean tube (0290). Cap and
mix. Insert tube into chamber, close lid and select SCAN SAMPLE. Record result.
10. Press and hold OFF button to turn spectrophotometer off or press EXIT button to exit
to a previous menu or make another menu selection.
TOTAL CHROMIUM WITH ACID DIGESTION PROCEDURE
1. Fill graduated cylinder (0418) to 50 mL line with sample water. Transfer to Erlenmeyer
fl ask (0431).
2. Use the 1 mL pipet (0354) to add 5 mL (fi ve measures) of *Sulfuric Acid, 5N (7681).
Swirl to mix.
3. NOTE: Highly buff ered waters may require pH adjustment. Adjust the pH of highly
buff ered samples to 7.0 ±0.5. Continue procedure.
4. Place fl ask on burner or hot plate. Bring solution to a gentle boil.
5. Fill pipet (0341) with Potassium Permanganate, 0.5% (7682). While gently swirling
fl ask, add Potassium Permanganate, 0.5% (7682), 2 drops at a time to boiling
solution, until solution turns a dark pink color which persists for 10 minutes. Continue
boiling.
6. Add one drop of *Sodium Azide, 5% (7683) to boiling solution. Boil for approximately
30 seconds. If pink color does not fade, add another drop of *Sodium Azide, 5%.
Continue adding *Sodium Azide, 5% one drop at a time until pink color disappears.
7. Remove fl ask from heat. Cool sample under running water. This is the digested
sample.
8. Pour digested sample into clean graduated cylinder (0418). Dilute to the 50 mL line
SMART Spectro 2 Test Procedures 05.02.16
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