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C. Wagner, B. Zachhuber, M. Kraft, A. Kenda, B. Lendl:
"Development of an IR-based Sensor for Aqueous CO2 in Beverages";
Poster: Infrared and Raman Discussion Group Christmas Meeting 07, London; 20.12.2007.

One of the main parameters for the quality control of beer and other beverages is the amount of dissolved carbon dioxide. At present a so called "volume expansion method" is used where the volume above the sample is expanded and the pressure of the gas is measured. One of the major disadvantages of this method is the dependency of the calibration on the beverage.
The absorption band of CO2aq is located at 2343 wavenumbers which is overlapped by the broad absorbance of the liberation mode of water. Furthermore this absorbance of water changes with different dissolved substances. With the IR measurement it will be possible to calculate the influence of the beverage on the water background and to correct the CO2 concentration. In that way a matrix independent measurement of CO2aq will be achievable. Another advantage of the IR measurement is the possibility for the simultaneous measurement of sugar concentrations.
To build an affordable small analyzer for CO2aq a new spectrometer, which is developed by the Carinthian Tech Research Center, is being tested. This spectrometer is based on the Czerny-Turner Monochromator principle. Instead of a normal grating driven by a stepper motor a scanning micro mirror with an optical grating is used.

http://publik.tuwien.ac.at/files/pub-tch_8200.pdf

Projektleitung Bernhard Lendl:
Schnelle spektrometrische Analyse von Flüssigkeiten unter Verwendung von miniaturisierten fluidischen Systemen