CO2 & NH3

Overview:

Carbon dioxide (CO₂) is a molecule composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure. Carbon dioxide is produced by all humans, animals, plants, fungi and microorganisms during respiration and is used by plants during photosynthesis. It is also generated as a byproduct of the combustion of fossil fuels and many other chemical processes.





Ammonia (NH₃) is normally encountered as a gas with a characteristic pungent odor. It contributes significantly to the nutritional needs of many organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia is also directly or indirectly a building block for the synthesis of many pharmaceuticals. Ammonia is both caustic and hazardous although is used widely.

Method:

Gas sensing electrodes typically work by allowing carbon dioxide (or ammonia) to diffuse across a permeable plastic membrane into the inner compartment of the electrode where they reversibly react with a buffer solution and in doing so alter the pH that the electrode senses. The electrodes are connected to standard pH meters or can be used with the ADInstruments ML165 pH Amp, which can also be used if a separate reference electrode is necessary.

Note: See also Respiratory Gas Analysis Page for CO₂ measurements in air.

Software:

LabChart
LabChart software (for Windows and Macintosh) combines the familiar simplicity of a traditional strip chart recorder with the powerful analysis features of a digital acquisition system. LabChart software and a PowerLab data acquisition unit provide data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Acquisition and analysis capabilities can be further increased with LabChart Extensions and LabChart Modules. LabChart Modules are available as part of LabChart Pro and LabChart Extensions are free for download from the website for existing LabChart users.

Electrodes can be calibrated using the Units Conversion feature of the software.

GLP and 21 CFR Part 11
For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.
 

Hardware:

Signal Conditioners
ML165 pH Amp
This amplifier is a dual front-end suitable for pH, ion selective, and temperature measurements in solution recordings. It is supplied with a RTD Temperature Probe. It can be used with:

• MLA060 Redox Electrode
• MLA042 pH Electrode
• MI-405 Miniature Glass Electrode for pH
• MI-409 Miniature Reference Electrode

Electrodes and meters made by Microelectrodes Inc, Diamond General and Thermo Orion may be suitable.

Transcutaneous carbon dioxide (TCpCO2) can be monitored by using skin electrodes. An approved electrically isolated meter must be used for human use. These meters can sometimes also monitor transcutaneous oygen levels. Manufacturers of these types of meters include Radiometer and SensorMedics.

Sleep-Disordered Breathing and School Performance in Children.
David Gozal, Pediatrics, 616-620, 1998

Transcutaneous PCO2 monitoring in the evaluation of hyperventilation of patients with recurrent nerve paralysis.
H. Miyazaki , H. Yamashita , T. Masuda , T. Yamamoto , S. Komiyama, European Archives of Oto-Rhino-Laryngology, S47-S50, 1999