Gas Analysis with TDLAS vs FTIR: A Comparison of Techniques

June 3, 2023

In the field of gas analysis, there are various techniques for measuring and monitoring gas content. Two common methods are TDLAS (Tunable Diode Laser Absorption Spectroscopy) and FTIR (Fourier Transform Infrared). In this blog post, we will compare these two techniques and discuss their advantages and disadvantages.

TDLAS (Tunable Diode Laser Absorption Spectroscopy):

TDLAS uses an adjustable laser to measure the absorption of gases in a sample solution. By changing the laser’s wavelength, it can be targeted towards specific gas molecules and measure their concentration. The advantages of TDLAS include high measurement accuracy, fast measurements, and the ability to measure multiple gases simultaneously. TDLAS is also less sensitive to interferences from other gases or humidity.

FTIR (Fourier Transform Infrared):

FTIR uses a broad-spectrum infrared light source and an interferometer to measure the absorption of infrared light by different gas molecules in a sample solution. By analyzing the resulting interference pattern, the gas composition and concentration can be determined. The advantages of FTIR include the ability to detect a wide range of gases and identify unknown compounds. FTIR is also flexible and can be used for both gas and liquid analysis.

Comparison between TDLAS and FTIR:

  • Measurement Accuracy: Both TDLAS and FTIR can offer high measurement accuracy for gas analysis. However, TDLAS has an advantage in terms of fast measurements and real-time monitoring.
  • Selectivity: TDLAS provides the ability to target specific gas molecules by changing the laser’s wavelength. FTIR, on the other hand, is more general and can detect a broader spectrum of gases.
  • Complexity: FTIR systems can be more complex to use and usually require calibration with reference gases. TDLAS systems are typically more user-friendly and require less maintenance.
  • Cost: FTIR systems can be more expensive than TDLAS systems, both in terms of the instrument itself and the operational costs.


Both TDLAS and FTIR are useful techniques for gas analysis, and the choice depends on specific requirements and applications. TDLAS offers high accuracy, fast measurements, and the ability to measure multiple gases simultaneously, while FTIR has the advantage of being able to detect a wide range of gases and identify unknown compounds. It is important to evaluate the needs carefully and choose the technique that best suits to achieve the desired gas analysis results. Consider factors such as measurement accuracy, selectivity, complexity, and cost when deciding between TDLAS and FTIR for your gas analysis needs.

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