Introduction
Atomic Absorption Spectroscopy (AAS) is a quantitative analytical technique that measures the concentrations of elements by detecting the absorption of optical radiation (light) by free atoms in the gaseous state.
AAS is widely used for the analysis of metals in various samples due to its specificity, sensitivity, and relatively simple instrumentation.
Principle
In AAS, a sample is atomized, and the ground-state atoms absorb light of specific wavelengths emitted by a light source.
The amount of light absorbed is proportional to the concentration of the element in the sample.
Process Steps
Atomization: The sample is introduced into a flame or graphite furnace where it is vaporized and converted into free atoms.
Radiation Source: A light source emitting the characteristic wavelength of the element of interest passes through the atomized sample.
Absorption: Ground-state atoms absorb specific wavelengths, reducing the intensity of the transmitted light.
Detection: The decrease in light intensity is measured by a detector.
Quantification: Using Beer-Lambert Law, the concentration of the element is determined.
Key Equations of Atomic Absorption Spectroscopy
Beer-Lambert Law in AAS:
Where:
A = Absorbance
I0 = Incident light intensity
I = Transmitted light intensity
ϵ = Molar absorptivity
c = Concentration of the analyte
l = Path length (usually constant in AAS)