Hach DR/850 Procedures Manual page 210

IRON, TOTAL,
9.
When the timer
beeps, place the
prepared sample into the
cell holder. Tightly
cover the ampul 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 iron will
be displayed.
Note: Standard Adjust may
be performed using a
prepared standard (see
Section 1).
Collect samples in acid-washed glass or plastic bottles. Adjust
the sample pH to 2 or less with nitric acid (about 2 mL per liter).
Store samples preserved in this manner up to six months at room
temperature. If reporting only dissolved iron, filter sample
immediately after collection and before addition of nitric acid.
Before testing, adjust the pH of the stored sample to between 3
and 4 with 5.0 N Sodium Hydroxide Standard Solution. Do not
exceed pH 5 as iron may precipitate. Correct the test result for
volume additions; see Correction for Volume Additions in
Section 1.
Standard Additions Method (Powder Pillows)
a) Snap the neck off a PourRite Iron Ampule Standard, 25 mg/L
Fe.
b) Use the TenSette Pipet to add 0.1 mL of standard to the
prepared sample measured in Step 10. Swirl to mix.
c) Measure the iron concentration as in Step 10. The
measurement does not require the three-minute waiting
period.
210