CO2 Retention Testing: FTIR Method
| Sample Type | Required Quantity | Equipment Used |
| Bottles | 14 |
Perkin Elmer FT-IR Spectrometer - Spectrum 2000 PTI LMS - Laser Measurement System |
Purpose
This procedure utilizes Fourier transform infrared spectroscopy to
measure the CO2 concentration within carbonated beverage
containers.
Description
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. During the first 10 days after
carbonation, the bottle is equilibrating. During this time, the CO2
is dissolving into both the bottle walls and the closure. In addition
the bottle is "creeping" by growing from the pressure of carbonation.
After 10 days, these processes have theoretically all reached
equilibrium so that there is no additional significant creep. The rate
of CO2 loss through the bottle and closure is now constant as
is the leak rate between the bottle finish and the closure liner.
Video Demonstration
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