This procedure utilizes Fourier transform infrared spectroscopy to measure the carbon dioxide concentration within carbonated beverage containers.
CO2 absorbs IR radiation in a very specific range of wavelengths. As the concentration of carbon dioxide decreases the measured CO2 absorption correspondingly decreases. The IR absorption value is divided by the length of the path through the container to account for the change in the container shape (there is usually a slightly shorter path length by end of test) over the time of the test. This calculation yields a concentration value for a particular sample. The concentration is then plotted against time to determine the rate of CO2 loss. The typical test time is 49 days with an interim report at 25 days.