Hach DR/700 Procedures Manual page 641

SULFIDE,
continued
10.
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.
ACCURACY CHECK
Standard Solution Method
Sulfide standard solutions are very unstable and should be prepared
from sodium sulfate and standardized as described in Standard Methods
for the Examination of Water and Wastewater, 17th ed., page 4-195.
STATISTICAL EVALUATION
A single operator repetitively tested samples of two laboratory prepared
solutions using one DR/700, matched sample cells and two
representative lots of testing reagents, Testing 0.595 mg/L S
concentration samples, the standard deviation was ±0.008 mg/L S
Testing zero concentration samples, the limit of detection was
2-
0.010 mg/L S . The limit of detection was calculated as three times the
standard deviation when testing zero concentration samples (Adapted
from Analytical Chemistry, 1980, 52, 2242-2249).
11.
Immediately
place the prepared
sample into the cell
holder.
Note: Typical indoor
lighting permits the
DR/700 to operate with
the cell compartment
cover open. In bright
sunlight, it may be
necessary to close the
cell compartment cover,
Transfer 10 mL of the
blank solution to a
10-mL cell. If the 10-mL
cell is used for the blank,
another 10-mL cell must
be used for the sample.
61-85
12.
Press:
READ
The display will
count down to 0.
Then the display will
show the results in
2-
mg/L sulfide (S ).
2-
2-
.