Atomic Absorption Spectroscopy (AAS) is an analytical technique used to determine the concentration of metal ions in a sample by measuring the light absorbed by free atoms in the gaseous state. It is highly sensitive and widely used in inorganic analysis.
Principle:
- Metal atoms in a sample absorb light of a specific wavelength that corresponds to the energy needed to excite electrons from a lower to a higher energy level.
- The amount of light absorbed is proportional to the concentration of the metal in the sample.
- This follows Beer-Lambert law, allowing quantitative determination.
Procedure:
- Sample Preparation: The sample is usually converted into a liquid solution.
- Atomization: The solution is vaporized in a flame or graphite furnace, producing free atoms.
- Light Source: A hollow cathode lamp specific to the metal emits light.
- Absorption Measurement: The free atoms absorb some light; a detector measures the amount of light absorbed.
- Calculation: The absorbance is compared with a calibration curve to determine the metal concentration.
Applications:
- Determining trace metals like lead, cadmium, zinc, and copper in water, food, and soil.
- Clinical analysis of blood or urine samples.
- Industrial quality control of metals in alloys and products.
- Environmental monitoring of pollutants.
Advantages:
- Very sensitive and accurate.
- Can detect very low concentrations of metals.
- Applicable to a wide range of metals.
Limitations:
- Requires expensive instrumentation.
- Only measures one element at a time.
- Sample preparation can be time-consuming.