Is FTIR affected by the environment?
It can be affected by water vapor or carbon dioxide. For example, if the water vapor or carbon dioxide level changes in the sample chamber or other parts of the light path between the time of the background measurement and the sample measurement, the absorption of the water vapor or carbon dioxide appears in the spectrum. This effect can be eliminated by minimizing the time between the background measurement and the sample measurement (minimizing time for environmental change to occur) or by purging the light path with dry air or high-purity nitrogen to obtain more stable environment. However, LabSolutions IR offers an atmosphere correction function to eliminate this effect. Apart from coping with environmental changes, purging is conducted to reduce water vapor and increase the amount of light, as measurements with no light loss due to water vapor are desirable to achieve highly accurate and sensitive measurement of small peaks appearing in the water vapor absorption region (4000 - 3400, 2000 - 1300 cm-1) in particular. The peaks of water vapor and carbon dioxide are shown below, for reference.