Hach DR2400 - Page 700

Selenium
Selenium
Page 2 of 8
Selenium_None_Other_DAB_Eng_Ody.fm
5. If you have not
distilled the sample, add
5.0 mL of Buffer Solution,
sulfate type, pH 2.0 to
each flask. Swirl to mix.
If the sample has been
distilled, adjust the pH of
the distillate to
pH 2.7 ±0.2 using 5 N
Sodium Hydroxide
Standard Solution
(Cat. No. 2450-32). Adjust
the blank to pH 2.7 ±0.2
using 5.25 N Sulfuric Acid
Standard Solution
(Cat. No. 2449-32).
6. Heat each flask on a
hot plate. Bring the
contents to a gentle boil.
7. Touch the timer icon.
Touch
OK.
A five-minute reaction
period will begin.
Continue to boil the
contents gently during
this time period.
A yellow color will
develop if selenium is
present.
8. When the timer
beeps, remove both
flasks. Cool to room
temperature using a
water bath.
Do not boil more than one
minute after the timer
beeps.
9. Transfer the contents
of each flask to separate
250-mL separatory
funnels. Label the funnels
“blank” and “sample”.
10. Add 2.0 mL of 12 N
Potassium Hydroxide
Standard Solution to each
funnel using a calibrated
1.0-mL plastic dropper.
Stopper. Shake each
funnel to mix.
11. Add 30-mL of toluene
to each funnel. Stopper.
Swirl and invert each
funnel, then open the
stopcock to vent the
funnel. Close the
stopcock. Repeat twice
with each funnel.
Use toluene only with
adequate ventilation.
12. Touch the timer icon.
Touch
OK.
A 30-second reaction
period will begin. During
this time, vigorously
shake the funnel that
contains the blank.
B S
B S
B S
B
B S B S B S
B