AAS is a type of atomic spectroscopy, which includes two other analytical methods: atomic emission and atomic fluorescence. The process of excitation and decay to the ground state is involved in all three methods. However, the difference between each technique is when the energy is measured. In atomic emission spectroscopy (AES), the energy emitted in the decay process is measured, while in AAS the energy absorbed during the excitation process is measured.

Atomic spectroscopy, and atomic absorption spectroscopy specifically, is commonly used in analytical chemistry, drug development, and industrial settings, and can perform both qualitative and quantitative analyses.

To obtain results, AAS uses the unique wavelengths that different atoms absorb to determine an element’s concentration in a liquid or solid sample, which is then compared to a standard, a previously recorded result of the same compound. It is a highly sensitive technique, and can measure concentration in parts per million (ppm) or parts per billion (ppb), enabling the detection of even trace elements in a sample.

AAS produces an absorption spectrum, which is recorded using an atomic absorption spectrometer. AA spectrometers typically include a flame burner—usually a hollow cathode lamp (HCL)—to atomize the sample, a monochromator, and a photon detector. AA Spectrometers that employ a flame burner are also referred to as flame atomic absorption spectrometers, employing flame atomic absorption spectrometry (FAAS or flame AAS) to obtain results. The detection limits of FAAS are of the order of 1–100 µg L−1, making it an excellent method of choice for determining minor and trace elements in liquid samples, or solid samples that have been converted to a liquid.

Depending on the model you’re interested in, some atomic absorption spectrometers come equipped with a turret or fixed lamp socket that holds multiple lamps to reduce downtime between samples or allow for sequential elemental analysis.

AAS can also be referred to as atomic absorption spectrometry, with the difference between the two being that spectroscopy is the study of how energy and materials interact, while spectrometry refers to how you apply spectroscopy as a measuring technique.