Differential optical absorption spectroscopy (DOAS) is a technique used to monitor atmospheric air pollutants. This form of spectroscopy is often used in continuous emission monitoring systems (CEMS).

Avantes instruments are integrated into a variety of CEMS around the world. Due to the high stability requirements of this technique, any of the Avantes thermo-electrically cooled spectrometers are used in this application.

Though it has been around for a few decades, nowadays, DOAS is performed by recording two absorption spectra, one as a reference scan through a column of the atmosphere (ideally) free of contaminants and one through an identical path length containing the impurity that needs to be analyzed. Trace contaminants partially absorb the light traveling through the measured atmosphere along the way, following Lambert Beer’s Law of Absorption.

Configuring a DOAS Setup

With DOAS, UV/VIS absorption can be used to measure a wide range of molecular species with a single broadband light source. Not only does DOAS decrease the cost of multi-species detection, it is also often far less expensive for single-species detection because of its use of inexpensive CCD spectrometers and a constant current UV/VIS emission lamp. In many cases, DOAS can be performed using direct or scattered sunlight.

Because of their high stability requirements, a cooled spectrometer like the AvaSpec-ULS2048x64TEC-EVO is an ideal choice for DOAS applications. For less demanding DOAS applications, our AvaSpec-ULS2048x64-EVO and AvaSpec-ULS2048XL-EVO are great lower-cost candidates.

Why choose Avantes for your DOAS application?

  • Thermoelectrically cooled spectrometers for high stability
  • Constant-current light sources for long-term measurements
  • Fast and accurate measurements
  • Extensive knowledge on DOAS and CEMS applications

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Application Examples

Below are detailed application notes on various uses of differential optical absorption spectroscopy in different applications and industries.

These are some of the products mentioned above. Contact one of our sales engineers for advice to find the perfect setup for your specific application.