AAS
Definition
Atomic absorption spectrometry. Free ground-state atoms in a vapour absorb a characteristic resonance wavelength from a hollow-cathode lamp, and Beer-Lambert converts the absorbance into a concentration.
- Full name
- Atomic Absorption Spectrometry (or Spectroscopy)
- Measures
- Concentration of specific metal elements in a sample
- How absorbance relates to concentration
- Directly proportional, following Beer-Lambert law
Common questions
How does AAS measure the concentration of a metal in a sample?+
AAS passes light of a specific wavelength through a sample containing vaporized atoms. The atoms absorb some of that light. The amount of light absorbed is proportional to how many atoms are present, following Beer-Lambert law. The instrument converts the absorbance measurement into a concentration value.
What is a hollow-cathode lamp and why is it used in AAS?+
A hollow-cathode lamp emits the exact characteristic wavelengths that ground-state atoms in the sample will absorb. Using the lamp tuned to each element's signature wavelength makes the measurement specific and sensitive to that element only.
What are the main variants of AAS, and when is each used?+
Flame AAS heats the sample in a flame to vaporize the atoms. Graphite furnace AAS uses a heated graphite tube for higher sensitivity with smaller samples. Cold vapor AAS works without heating, used for elements like mercury that are volatile at room temperature or require special handling.
Related terms
- GFAAS
- Graphite-furnace AAS, also called electrothermal AAS. A graphite tube heated electrically through a programmed ramp atomises a microlitre aliquot, giving roughly 100...
- Background Correction
- A method (deuterium continuum, Zeeman effect, Smith-Hieftje self-reversal, or high-resolution continuum-source) that subtracts non-atomic absorption (molecular bands, scatter) from the raw absorbance...
- CRM
- Certified reference material. A matrix-matched material of known composition (NIST SRM 955c lead in caprine blood, SRM 1577c bovine liver) used to...
- CVAAS
- Cold-vapour AAS. Mercuric ions are reduced by stannous chloride or sodium borohydride to elemental mercury vapour, swept by argon into a quartz...
- HG-AAS
- Hydride-generation AAS for hydride-forming elements (As, Sb, Se, Bi, Te, Sn, Ge). Sodium borohydride in acid generates the volatile hydride, which is...
- Hollow Cathode Lamp (HCL)
- A sealed lamp whose cathode is made of the element being analysed, filled with argon or neon at low pressure. Strikes a...
- ICP-MS
- Inductively coupled plasma mass spectrometry: the laboratory reference method for trace element quantification in food matrices. Uses high-temperature argon plasma to atomise...
- ICP-OES
- Inductively coupled plasma optical emission spectrometry: the plasma excites atoms which emit element-specific wavelengths of light on returning to ground state; suited...
- Ion Chromatography
- Ion-exchange separation with conductivity detection after a suppressor, used to quantitate inorganic anions and cations such as fluoride, oxalate, sodium and calcium.
Explained in these topics
- Atomic Absorption Spectrometry: Flame, Graphite Furnace, Cold VapourAtomic absorption spectrometry. Free ground-state atoms in a vapour absorb a characteristic resonance wavelength from a hollow-cathode lamp, and Beer-Lambert c...
- Inorganic Poison Analysis: AAS, ICP-OES, ICP-MS and Ion ChromatographyAtomic absorption spectroscopy. Ground-state atoms in a vapour absorb characteristic wavelengths from a hollow-cathode lamp; absorbance is proportional to conc...