Thermo Fisher Scientific Dioxide Ion Selective Electrodes Carbon User Manual
Page 13
Instruction Manual
Carbon Dioxide Electrode
13
ELECTRODE APPLICATION
Carbon Dioxide Content of Wines and Carbonated Beverages
Wines and carbonated beverages have a high (greater than 2X10
-2
M or 880 ppm) carbon dioxide
concentration. As a result, samples are measured after dilution. When samples are collected, they
must be made basic immediately or CO
2
will escape into the atmosphere (see
Sample Storage
section). After diluting the sample, it must be acidified with carbon dioxide buffer. The carbon
dioxide concentration is determined by direct measurement (see
MEASUREMENT
section). Finally,
the original carbon dioxide concentration is calculated, taking the dilution factor into account.
The required equipment and solutions are found in
Required Equipment
and
Required Solutions
.
In addition, pH Adjustment Solution, 10M NaOH, is required.
To measure a sample:
1.
Calibrate the meter according to the directions in the
MEASUREMENT
section.
2.
Add enough 10M NaOH solution to adjust the pH of the sample above 10
immediately when the sample container is opened.
3.
To a 100 ml volumetric flask, quantitatively transfer 10 ml of the alkaline sample to
the flask and fill to the mark with distilled water. After agitating the flask to mix the
contents, transfer the solution to a 150 ml beaker.
4.
Place the beaker on the magnetic stirrer and begin stirring at a constant rate. Add 10
ml of carbon dioxide buffer. Lower the tip of the electrode in the solution. Record
the mV reading when stable. Determine the measured concentration from the
calibration curve.
5.
Using the following formula, determine the carbon dioxide sample concentration:
Vs + VNaOH
Cs = 10 X ——————— X Cm
Vs
where: Cs = sample concentration
Vs = sample volume before adding NaOH
VNaOH = volume of NaOH added to sample
Cm = measured concentration
Example: Assume 12 ml of 10M NaOH was added to 360 ml of sample. The total volume would
then be 372 ml. Add 10 ml of this mixture to a 100 ml volumetric flask. Dilute to the mark with
distilled water. By taking into account the addition of base to the sample and the sample dilution,
the measured concentration is related to the actual sample concentration:
Cs = 10 X 360+12 Cm
360
Cs = 10.33 Cm