M-75: Aspects of optical and traditional measurement of dissolved carbon dioxide by in-line, at-line, and laboratory instrumentation

J. BLODER (1), J. Northrop (2); (1) Anton Paar GmbH, Graz, Austria; (2) Anton Paar USA, Ashland, VA, U.S.A.


Optical measurement technology in general is becoming more common in process environments, especially in the brewing and beverage industry, and offers many benefits, such as ease of installation, cleaning, and compact size. Optical sensors also have no moving parts and are considered maintenance-free. Most of the methods used for CO2 measurement in the laboratory are based on Henry’s and Dalton’s law. This poster deals with the aspects of optical versus traditional measurement of dissolved CO2 and how/whether both of those measurement principles can be employed together for quality checks in the beverage production process. At-line and laboratory instruments may combine the classical method of CO2 analysis according to Henry’s law with the multiple volume expansion method, which makes use of the fact that the solubility of CO2 in beverages is much higher than the solubility of air. The solubility coefficients of each beverage type are predefined in the CO2 meter. A selective optical sensor for measuring CO2 in liquids uses infrared ATR (attenuated total reflectance) spectroscopy. However, a very small influence of the sample composition (alcohol, extract, etc.) is still present. To eliminate this residual influence, a special calibration model can be applied. As reference for the factory adjustment, the laboratory measurement is used. In-line, at-line, and laboratory instrumentation may show small deviations in their results. This poster will analyze the reasons for the deviations and show how large they can be and what can be done to minimize them. The results of a head-to-head comparison, ease of use in daily routine, and measurement performance (repeatability) of the instruments/methods will be discussed.

Josef Bloder received his M.S. degree in electrical engineering from the Technical University of Graz in Styria, Austria, with a focus on biomedical engineering. He has been with Anton Paar since 1987 in various positions and is an expert in the field of process instrumentation and technology. After many years as product manager, he is now applying his expertise as key projects manager for process instruments and developing new applications and technologies in new and existing industries.

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