17
7. The procedure can be repeated with a second standard
addition to verify slope and operation of the method.
Note:
This method is preprogrammed in the Hanna HI
4222pH/ISE/mV meter, which simplifies the method
greatly and permits repeated determinations easily.
Example:
Carbon Dioxide determination with known addition:
1. A 50 mL sample of unknown (V
SAMPLE
) is placed in an
clean vessel with an electrode. 5 mL of ISA is added
to the sample . The sample is covered and permitted
to mix throughly and continueously. The mV is then
recorded when the sensor has stabilized.
2. 5 mL (V
STANDARD
) of 0.1 M (C
STANDARD
) standard is then
added to the vessel and is permitted to mix. The mV
value increases as the concentration increases. (Note:
for other concentration samples, add a known volume
and concentration of standard to produce a 30 mV
change or greater.
3. The unknown carbon dioxide concentration in the
original sample (C
SAMPLE
) can then be determined by
using the equation provided.
.
Содержание HI 4105
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