Atomic Absorption Spectroscopy (AAS) is an analytical technique used to determine the concentration of specific metal elements in a sample. It is highly sensitive and widely used in chemistry, environmental analysis, clinical labs, and metallurgy. Here’s a clear explanation:
Principle
AAS is based on the absorption of light by free atoms in the gaseous state. Each element absorbs light at a specific wavelength. The amount of light absorbed is directly proportional to the concentration of that element in the sample.
- The sample is usually converted into free atoms by heating (often in a flame or graphite furnace).
- A light source, usually a hollow cathode lamp specific to the element of interest, emits light of a wavelength that matches the absorption spectrum of that element.
- As light passes through the atomized sample, some of it is absorbed. The detector measures the decrease in light intensity.
Components of AAS
- Light Source: Hollow cathode lamp specific to the element.
- Atomizer: Converts the sample into free atoms (Flame or Graphite Furnace).
- Monochromator: Isolates the specific wavelength of interest.
- Detector: Measures the intensity of transmitted light.
- Readout System: Calculates concentration based on absorption.
How it Works
- The sample solution is aspirated into a flame or graphite furnace to form free atoms.
- The lamp emits element-specific light through the atomized sample.
- Atoms of the element absorb some of the light.
- The detector measures how much light is absorbed.
- Using a calibration curve, the concentration of the element is determined.
Applications
- Measuring metal concentrations in water, soil, and biological samples.
- Monitoring trace metals in food and pharmaceuticals.
- Quality control in metallurgy and chemical industries.
AAS is highly precise, sensitive, and selective, but it is mainly limited to metallic elements and cannot detect non-metals.