Hach DR/850 Procedures Manual page 80

BROMINE,
continued
9.
After the timer beeps,
place the AccuVac
ampul into the cell
holder. Tightly cover the
ampule with the
instrument cap.
Sampling and Storage
10.
Press:
READ
The cursor will move to
the right, then the result
in mg/L bromine will
be displayed.
Note: If the sample
temporarily turns yellow
after reagent addition, or
the display flashes "limit",
it is due to high bromine
levels. Dilute a fresh sample
and repeat the test. A slight
loss of bromine may occur
during dilution. Multiply
the result by the dilution
factor; see Section 1.
Analyze samples for bromine immediately after collection.
Avoid plastic containers since these may have a large bromine
demand. Pretreat glass sample containers to remove any
bromine demand by soaking in a dilute bleach solution (1 mL
commercial bleach to l liter of deionized water) for at least 1
hour. Rinse thoroughly with deionized or distilled water. If
sample containers are rinsed thoroughly with deionized or
distilled water after use, only occasional pretreatment is
necessary.
A common error in testing for bromine is introduced when a
representative sample is not obtained. If sampling from a tap, let
the sample flow for at least 5 minutes to ensure a representative
sample. Let the container overflow with the sample several times,
then cap the sample container so there is no headspace (air) above
the sample. If sampling with a sample cell, rinse the cell several
times with the sample, then carefully fill to the 10-mL mark.
Note: Standard Adjust may
be performed using a
prepared standard
(see Section 1).
80