CB (E7) 06/2018 Page 131/174
4
6
8
10
12
14
16
18
2
3,70
g/l NaHCO
3
2,20
g/l NaHCO
3
0,85
g/l NaHCO
3
6.8
7.0
7.2
7.4
7.6
Value pH
Vo l. % C O
2
0,35
g/l NaHCO
3
1,20
g/l NaHCO
3
Trade names of common media:
DMEM
BME
MEM
Medium 199
Mc Coy
F10
3
3.70
2.20
2.20
2.20
2.20
1.20
Figure 28: Value pH of NaHCO
3
buffered media as a function of the CO
2
concentration:
Example: If a pH of 7.2 is measured in a medium buffered with 2.20 g NaHC0
3
per liter, there must be
8 vol.-% CO
2
surrounding this medium.
19.1.2 Measuring CO
2
directly via chemical indicator tubes
This is a common “do-it-yourself” test for many users. A chemical color reaction in a glass tube shows the
CO
2
concentration. A standardized volume of air from inside the incubator has to be suctioned through
this glass tube to get a quantitative test result. Therefore, use a special hand pump with a standardized
suction volume.
Procedure (example):
All the necessary equipment must be supplied by one manufacturer only and in a defined test system.
Note: These test systems are not very accurate. A typical accuracy is around 10 % of the full-scale value.
These test systems are not suitable for calibrating the BINDER sensor system.
19.1.3 Measuring CO
2
directly with an electronic infrared measuring device
Another possible way of measuring the CO
2
concentration is by electronic sensor systems. Portable
measuring devices are suitable for measuring temperature and CO
2
concentration and can be used both
for reference measurements in certified laboratories, and for service purposes.
19.2 Temperature reference measurement
When performing a temperature reference measurement using an electronic measuring, and temperature
display device, it is important to use a device traceable to an acknowledged standards/calibration
institution (DKD, PTB for Germany) with a valid calibration certificate.
Note: The cable of the sensor must be thin enough to lay it over the door gasket of the incubator without
causing any leakages.
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