Hach DR/850 Procedures Manual page 216

MANGANESE, High Range,
9.
Place the prepared
sample into the cell
holder. Tightly cover the
sample cell with the
instrument cap.
Sampling and Storage
Accuracy Check
continued
10.
Press:
READ
The cursor will move to
the right, then the result
in mg/L manganese will
be displayed.
Note: Standard Adjust may
be performed using a
prepared standard (see
Section 1).
Collect samples in acid-washed plastic bottles. Manganese may
be lost by adsorption to glass container walls. Adjust the pH to
less than 2 with nitric acid (about 2 mL per liter). Preserved
samples may be stored up to six months at room temperature.
Adjust the pH to 4 to 5 with 5.0 N sodium hydroxide before
analysis. Do not exceed pH 5, as manganese may be lost as a
precipitate. Correct the test result for volume additions; see
Correction for Volume Additions in Section 1 for more
information. If only dissolved Mn is to be determined, filter
before acid addition.
Standard Additions Method
a) Snap the neck off a Manganese Voluette Ampule Standard
Solution, 250 mg/L Mn.
b) Use the TenSette Pipet to add 0.1, 0.2 and 0.3 mL of
standard, respectively, to the three 25-mL water samples.
Swirl to mix.
c) Transfer only 10 mL of each solution to the 10-mL sample
cells.
d) Analyze each standard addition sample as described in the
procedure. The manganese concentration should increase
1.0 mg/L for each 0.1 mL of standard added.
216