Important: Please monitor the pH of the solution over the time course of the calibration to ensure
that it remains at 4 or lower. Add more HCl into the solution if pH increases above 4. At pH above 4
dCO
2
will be converted back into bicarbonate and will no longer be measured by the probe (Fig. 28).
Fig. 28 Carbon Dioxide – Carbonic Acid Equilibrium.
• CO
2
calibration can be performed by PBR software. Please refer to the PBR Software Manual.
• The frequency of recalibration operations depends on the degree of accuracy required and on the measuring
conditions. The CO
2
probe should be re-calibrated when the experimental temperature is different from the one
used during the calibration. If temperature is not changed, we recommend re-calibration every three months or
at the least one point calibration check for verification purposes.
Fig. 29 Typical CO
2
calibration curve. Right: Exponential fir equation with depicted constants a and b.
Example of resulting µM concentration of dissolved CO
2
in the vessel when air with 400 to 15,000 ppm CO
2
content is used
to bubble the water. Please note that the values are only for demonstration purposes and will depend on temperature,
atmospheric pressure and gas flow rate.
To Next Page
Loading...