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Working of FTIR Gas Analyzers

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Working of FTIR Gas Analyzers

FTIR (Fourier Transform Infrared Spectroscopy) gas analyzer is a highly sophisticated instrument used to analyze the presence and concentration of different molecules in a gas sample. Its working principle is based on infrared spectroscopy technology.


Here’s how an FTIR gas analyzer works:

How FTIR gas analyzers work

  • The light source produces infrared light: The core of an FTIR instrument is a light source, usually a white light source with stable intensity. This light source produces a broad spectrum of light including visible and infrared light.


  • The beam passes through the sample: The beam of the infrared spectrometer passes through the gas sample to be measured. This gas sample can be a gas or a gas mixture and is usually placed in a gas absorption cell or gas chamber.


  • Absorption phenomena occur: Gas molecules in the sample interact with specific wavelengths of infrared light. These molecules absorb energy from infrared light, causing their vibration, bending, or stretching patterns to change. Different types of gas molecules have specific absorption lines for infrared light of different wavelengths, and these lines are fingerprints of their molecular structures.


  • Spectral scan: FTIR instruments gradually change the wavelength of infrared light by scanning the entire infrared spectrum. This process usually uses a technique called “interferometry”, which changes the optical path difference and therefore the wavelength by introducing a movable mirror.


  • Fourier transform: After the laser scan, the FTIR instrument performs a Fourier transform on the light signal reflected or transmitted back from the sample. This transformation converts a signal in the time domain (light intensity over time) into a signal in the frequency domain (wavenumber or wavelength of light). This process produces an image called a spectrogram, which contains information about the intensity of light at various wavelengths.


  • Spectral analysis: The spectral plot shows absorption peaks at different wavelengths. By comparing the absorption peaks of the sample with a library of known gas molecule spectra, the presence and concentration of different gas components in the sample can be determined.


  • Data analysis: Finally, the instrument’s software performs data processing and analysis to provide accurate gas component concentrations, typically expressed in “wavenumbers” (in cm^-1).


Read more: https://esegas.com/analyzing-industrial-gas-emissions-and-production-using-ftir-gas-analyzers/


The working principle of FTIR gas analyzers is based on the absorption of infrared light of specific wavelengths by gas molecules. By measuring the intensity of light absorption at different wavelengths, the instrument can determine the concentration of different molecules in a gas sample, enabling precise gas analysis. This technology has the advantages of high sensitivity, high resolution and the ability to analyze multiple gas components simultaneously, so it is widely used in fields such as environmental monitoring, industrial control and chemical analysis.

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