Absorption Spectroscopy

Last updated: September 3, 2019

What Does Absorption Spectroscopy Mean?

Absorption spectroscopy is a form of materials analysis that is used to identify the chemical composition of a compound by measuring its interaction with a source of electromagnetic radiation (e.g., light).

By firing radiation at a sample and recording the resulting changes in the wavelength/frequency of the radiation, it is possible to understand what elements of the radiation were absorbed by the sample and what elements passed through it unimpeded. As different chemicals absorb different types of radiation, this information can be used to determine what chemical substances the sample contains.

Safeopedia Explains Absorption Spectroscopy

Absorption spectroscopy is used by industrial hygienists and other occupational safety professionals to assess what chemical substances are present in a given environment. This makes the technique useful for determining whether workers have been exposed to any hazardous substances. Additionally, many toxic gas detectors use absorption spectroscopy to detect the presence of harmful gases.

Absorption spectroscopy is effective because all chemical substances have absorption spectrums that are specific to their particular physical and electronic properties. This means that a given chemical, when exposed to radiation, will only ever absorb energy from a specific fraction of the frequencies that the radiation contains. Because a specific chemical will always absorb the same frequencies, it is therefore possible to determine what substances are present in a sample by determining what radiation frequencies the sample has absorbed.

For instance, a portable gas detector that uses absorption spectroscopy to detect the presence of a specific toxin would do so by firing an infrared light through the environment being evaluated and toward a sensor. The sensor would quantify the difference between the light sent and the light received, and then it would use that information to determine if the toxic gas is present. These devices are generally designed to ignore any light absorption caused by expected atmospheric gases, such as oxygen.

Absorption spectroscopy can, in certain situations, be a hazardous process. Atomic absorption spectroscopy involves burning a sample, which may lead to a risk of explosion or the release of a toxic gas if done improperly and with certain hazardous chemicals. Portable gas detectors and other general-use chemical detection devices do not pose this risk.


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