The process of instrumental analysis technique for tracing metal analysis is known as Atomic Absorption Spectroscopy. The light absorption by element-specific wavelength is done by ground-state atoms, either in the electrothermal graphite furnace or the flames.
The applications of this technique include the analysis for trace metals in lakes, soils, rivers, oceans, beverages, food, beverages, biological fluids, geological and mineralogical samples, specimens, and even forensic analysis. The results are obtained in ppm levels, especially when using graphite furnace atomization.
The uses of AAS include many, and the primary use of them is to provide viable and cheaper solutions to trace the number of metals in the sample. The samples include natural and human-made ones, especially environmental samples, pharmaceutical samples, biological samples, agricultural samples, soil, and even food and drinking water.
There are also the advantages of sensitivity, precision, and speed over the usual gravimetric methods. Various other accessories were introduced, such as the graphite furnace, improvements in the suppression of matrix interferences, and flow injection analysis. All of these have helped to improve the selectivity and sensitivity of the analytes in the matrices.
Principle of ASS
The techniques to analyze trace metals have been evolved to sophisticated instrumental techniques, which are time-saving also. It has become a technique where one can afford the operational costs as well as involve sensible investment.
It has even helped install the equipment necessary for atomic absorption spectroscopy in colleges and industries, making it easily accessible.
In talking about the principle of AAS, it is based on the ability of free atoms to absorb light at the ground state at a specific wavelength. The wavelengths give better specifications to the technique and detection ability during the process. The applications of AAS include the following:
- It helps detect the presence of Lead in Paint
- Quantitative analysis of metal concentration in solutions.
- Trace the presence of elements in raw materials or products along with ICP-MS
- Trace metals in industrial effluent streams.
- Low-level contaminants’ analysis.
Working of Atomic Absorption Spectrometer
As mentioned above, the instrument works on the principle of light absorption to measure gas-phase atoms in the metals. Light is focused on a flame, and a hollow cathode lamp produces it. On the inside of the lamp, there is an anode as well as a sample.
A high voltage is made to pass through the cathode and the anode. Later, the metal atoms become excited, and they produce light with a particular emission spectrum.
As we know, atoms consist of a core that has protons and neutrons. Surrounding it are many electrons, which are bound to the center at varying energy levels. As the electron changes from a particular energy level to a lower one, one photon is released.
It is equivalent to the energy released by the reduced level of the electron. It causes the photon to form an atomic spectral line.
The frequency (v) of these spectral lines is linked to the energy (E) released. According to Planck’s law, E= hv; and ‘h’ is known as Planck’s constant. The radiation produced by the atoms is characteristic of both their emission and absorption coefficients.
The quantity of energy emitted can be deleted, and the quality of energy put into the flame. With these two, it is possible to calculate the number of elements present in the mixture.
Metals that can be detected using AAS
- Aluminium Al
- Arsenic As
- Antimony Sb
- Barium Ba
- Beryllium Be
- Chromium Cr
- Calcium Ca
- Cobalt Co
- Cadmium Cd
- Gallium Ga
- Copper Cu
- Hafnium Hf
- Indium In
- Iron Fe
- Lead Pb
- Magnesium Mg
- Lithium Li
- Mercury Hg
- Manganese Mn
- Niobium Nb
- Molybdenum MoNickel Ni
- Ruthenium Ru
- Tungsten W
- Tin Sn
- Zinc Zn
- Vanadium V
- Zirconium Zr
Applications of AAS
The metal contaminations of industrial effluents in the rivers, lakes, and oceans can be found using this technique. Thus, one can find out the safety of water for drinking and other commercial purposes using this method. The AAS is a recognized method set by regulatory bodies to find out the safety limits of samples.
The identification of gemstones is made possible by finding the presence of trace metals in them. The elemental combination of archaeological artifacts has proven itself to be very helpful to trace their source.
The trace metal analysis technique plays a vital role in the formulation of development, catalyst efficiency, and dosage limits of the samples. They help in setting the prescribed limits of the elements, beyond which it can be harmful.