Atomic Absorption Spectroscopy (AAS)
What is Atomic Absorption Spectroscopy?
Atomic Absorption Spectroscopy (AAS) is an instrument or analysis technique in analytical chemistry for rapid trace metal analysis. AAS methods depend upon the absorption of light by atoms.
It is based on the absorption of light with a specific wavelength by ground state atoms of elements in the flame or electrothermal graphite furnace. It analyzes elements in either liquid or solid samples through the application of characteristic wavelengths of electromagnetic radiation from a light source.
Atoms absorb light at a definite wavelength depending upon the nature of the chemical elements. For example, sodium is absorbed in 589 nm, uranium is absorbed in 385.5 nm, and potassium is absorbed in 766.5 nm. It uses widely in the analysis of trace metals in soils, lakes, rivers, oceans, drinking water, pharmaceuticals, foods and beverages, geological and mineralogical samples, petroleum products, biological fluids and specimens, and forensic analysis.
Uses of the AAS technique
Atomic absorption spectroscopy (AAS) instrument is a powerful tool for analysis. It is popular with analysts for several reasons. The AAS technique provides advantages of speed, sensitivity, and precision over the classical gravimetric methods.
- The most important is the speed at which the analysis can be carried out. If the analyst is confronted with the problem of analyzing several samples within a day. Such a type of analysis is possible with the AAS instrument.
- It determines and analyzes all the elements at trace concentration.
- It is not always essential to separate the elements before analysis because it is possible to determine one element in presence of another.
- It provides a high degree of accuracy and precision in the results of the analysis. It contributed to the widespread presence of atomic absorption spectrometers in college laboratories, industrial laboratories, and regulatory body laboratories across the world.
AAS has an unlimited number of uses and is still a popular choice of analysts for uncomplicated trace elemental analysis. Flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) is widely accepted in many industries and these are comparatively inexpensive instruments in trace metal analysis.
Instrumentation of AAS
Any AAS instrument is composed of the following three main components:
- Atomizer
- Radiation Source
- Spectrometer
Atomizer
Atomization is an important step in AAS and can be carried out either by a flame or furnace. Heat energy is used to convert the metallic element to atomic dissociated vapour.
The temperature should be controlled carefully to convert it to an atomic state because at too high or too low a temperature, atoms will be ionized and will not be absorbed. Flame and electrothermal atomizers are two commonly used atomizers for AAS instruments.
Radiation Source
There is a radiation source in AAS that irradiates the atomized sample. The analyzed sample absorbs some of the radiation, and the rest passes through the spectrometer to a detector. Line sources and continuum sources are two radiation sources in the AAS instrument.
Line sources excite the analyte and provide its own line spectrum. Continuum sources provide the spectrum over a wider range of wavelengths.
Spectrometer
A spectrometer in AAS instruments is used to differentiate between various types of wavelengths of light before they pass to the detector. The spectrometer in the AAS instrument can be either single-beam or double-beam.
The radiation is directed through the atomized sample in single-beam spectrometers but double-beam spectrometers require two beams of light — one beam that passes directly through the sample, and another that does not pass through the sample at all.
Atomic Absorption Spectroscopy Applications
Atomic absorption spectroscopy (AAS) provides cost-effective solutions for the analysis of trace amounts of metals from geological samples, environmental samples, biological specimens, agricultural products and soils, pharmaceuticals, foods, and drinking water.
- Geological samples: The elemental composition of minerals and rocks provides important information on commercial refining operations. After mining, the ores and minerals may be tested by an AAS instrument for determining their composition.
- Environmental Monitoring: Environmental monitoring for trace metal contamination by atomic absorption spectroscopy (AAS) from industrial effluents, oceans, rivers, and lakes gives important data about the safety of drinking water and water that use for commercial purposes.
- Materials Development: AAS analysis provides the composition of materials that significantly influenced some common properties of such as hardness, brittleness, grain size, crystallinity, and amorphous nature.
- Pharmaceuticals: AAS analysis plays an important role in formulation development, catalyst efficiency, and dosage limits in the pharmaceutical industry. Most elements have a beneficial role up to certain prescribed limits but beyond such limits, many serious side effects are caused by these elements.
- Foods and Beverages: Food safety is increasing day by day. Food manufacturers have to ensure that trace metals do not exceed the permissible limits. Therefore, the foods and beverages industry uses atomic absorption spectroscopy and other sophisticated instruments for ensuring their quality.
- Agriculture: The constitution of soils and their acidic or basic nature is essential for productivity and nutrient value. AAS analysis on plants gives a fair idea of how the uptake of minerals gets distributed under different growth conditions.
- Forensics: Atomic absorption spectroscopy (AAS) analysis provides valuable information on specimens collected from the scene of a crime.
References
- Atomic Absorption Spectroscopy — Instrumentation, Principle — Priyamstudycentre.com
- Atomic absorption spectroscopy — Wikipedia
- Atomic Absorption Spectrometry (AAS) Information — thermofisher.com
