Atomic Absorption Spectroscopy
Definition and meaning of Atomic Absorption Spectroscopy in chemistry.
Atomic absorption spectroscopy (AAS) is an analytical technique that measures the concentration of specific elements in a sample by detecting the absorption of light by free ground-state atoms. The amount of light absorbed is directly proportional to the element's concentration.
In more detail
In AAS, a sample is atomized using a flame or graphite furnace, converting it into individual atoms capable of absorbing ultraviolet or visible light. A hollow cathode lamp produces light at a wavelength specific to the element being analyzed. As this light passes through the atomized sample, the element's atoms absorb a portion of it. A detector measures the transmitted light intensity, and the absorbance, the difference between incident and transmitted light, is plotted against standard solutions to quantify the element's concentration.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Detection Range | Parts per billion to parts per million |
| Wavelength Range | 190–900 nm (ultraviolet-visible) |
| Chemical Formula | Depends on analyte element |
To determine lead concentration in drinking water, a water sample is aspirated into an air-acetylene flame at about 2300°C. A lead hollow cathode lamp emits light at 283.3 nm, which the atomized lead absorbs. The measured absorbance is compared to a calibration curve made from known lead standards, yielding the exact concentration in the sample.
Frequently asked questions
What elements can AAS detect?
AAS detects most metallic elements including copper, zinc, iron, lead, chromium, and cadmium, as well as some metalloids, but not nonmetals like nitrogen or oxygen.
How does AAS differ from inductively coupled plasma-mass spectrometry (ICP-MS)?
AAS measures ground-state atoms absorbing light at characteristic wavelengths, while ICP-MS ionizes atoms and measures mass-to-charge ratios. ICP-MS is generally more sensitive but AAS is simpler and more cost-effective.