Hach DR/700 Procedures Manual page 462

CHROMIUM, TOTAL,
16.
Press:
ZERO
The display will
count down to 0.
Then the display will
show 0.000 mg/L and
the zero prompt will
turn off.
SAMPLING AND STORAGE
Collect samples in a cleaned glass or plastic container. Adjust the pH to
2 or less with nitric acid (about 2 mL per liter). Preserved samples can
be stored for at least 6 months at room temperature. Before analysis,
adjust the pH to 4 with 5.0 N Sodium Hydroxide Standard Solution.
Correct for volume additions; see Sampling and Storage, Volume
Additions, (Section I) for more information.
continued
17.
Place the
prepared sample in
the cell holder.
Note: Typical indoor
lighting permits the
DR/700 to operate with
the cell compartment
open. In bright
sunlight, it may be
necessary to close the
cell compartment cover.
Transfer 10 mL of the
blank and 10 mL of the
sample to a
10-mL sample cell and
proceed.
55-14
18.
Press:
READ
The display will
count down to 0.
Then the display will
show the results in
mg/L chromium.
Subtract the
ChromaVer 3
Reagent blank value
for final
concentration; see
note below.
Note: Determine a
reagent blank for each
new lot of ChromaVer 3
Reagent as follows:
Repeat steps 9 to 18
using demineralized
water as the sample.
Subtract this value from
each result obtained
with this lot of reagent.