Nutrients are the substances which after ingestion, digestion, absorption and assimilation, become a part of cell and thus maintains all cellular activities in the body. Minerals are one of such nutrient. Some minerals are essential for cellular metabolism. There are thirteen minerals considered as ‘essential’ viz., calcium, phosphorous, magnesium, sodium, potassium, iron, manganese, zinc , copper, selenium, chromium, cobalt and iodine.

1. MS. Ankita Avinash More
GATE, SET
Atomic absorption spectrometry
(AAS)
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2. Nutrients are the substances which after ingestion, digestion, absorption and
assimilation, become a part of cell and thus maintains all cellular activities in the body.
Minerals are one of such nutrient. Some minerals are essential for cellular metabolism.
There are thirteen minerals considered as ‘essential’ viz., calcium, phosphorous,
magnesium, sodium, potassium, iron, manganese, zinc , copper, selenium, chromium,
cobalt and iodine.
These minerals are again classified depending upon their requirements in the body;
macro minerals and micro or trace minerals.
When body requires more than 100 mg of a mineral in 1 day then it is considered as
macro minerals viz., calcium, magnesium, phosphorus, sodium and potassium.
The minerals whose requirement is less than the said level will considered as trace
minerals. Zinc, Iron, Manganese, Selenium, Copper, Cobalt are the trace minerals.
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3. Atomic absorption spectrometry (AAS) detects elements in either liquid or solid
samples through the application of characteristic wavelengths of electromagnetic
radiation from a light source. Individual elements will absorb wavelengths
differently, and these absorbances are measured against standards.
Depending on the light wavelength and its intensity, specific elements can be
detected and their concentrations measured.
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5. Principle
The basic principles of AAS can be expressed as follows. Firstly, all atoms or
ions can absorb light at specific, unique wavelengths. When a sample containing
copper (Cu) for example, is exposed to light at the characteristic wavelength of
Cu, then only the Cu atoms or ions will absorb this light. The amount of light
absorbed at this wavelength is directly proportional to the concentration of the
absorbing ions or atoms.
When the atom is exposed to its own unique wavelength, it can absorb the
energy (photons) and electrons move from a ground state to excited states.
Furthermore, since the electronic structure of every element is unique, the
radiation absorbed represents a unique property of each individual element and it
can be measured.
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6. Atomic absorption spectroscopy (AAS) determines the concentrations of minerals in
samples.
It is a process involving the absorption by free atoms of an element of light at a
wavelength specific to that element. This method is very sensitive and enables to detect
small amount of an element of 1 ppm using flame procedure.
Lower levels can be determined down to 0.001ppm using graphite furnace procedure. In
their elemental form, metals will absorb ultraviolet light when they are excited by heat.
For all non conducting elements (insulators) and for most of the electrons in atoms of
conducting elements, the energy gap between ground state and first or higher energy level
is very large. So, very energetic photons are required. Vacuum UV or X-ray is required to
excite the atom.
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7. Instrumentation-
An atomic absorption spectrometer uses these basic principles and applies them in practical
quantitative analysis. A typical atomic absorption spectrometer consists of four main
components:
1. light source
2. atomization system
3. monochromator
4. detection system
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8. Working-
sample solution is aspirated into the spray chamber through capillary tube. The
liquid sample is aerolized and mixed with combustible gases such as acetylene and
nitrous in the spray chamber and burned in a flame .
The individual atoms of the sample are released to form a cloud inside the flame.
The atoms of the element get free.
To bring it from ground state into an excited state by passing UV light is required
through hollow cathode lamp. On absorbing UV light at specific wavelengths the
ground state metal atoms get transitioned to higher electronic state.
The region of the spectrum to be measured is selected by a monochromator.
The isolated spectral line falls on the detector and the output is amplified
and sent to a readout device meter, digital or analogue or through a computer data
processing system. The data is processed through software.
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12. Sample Preparation
There are at least five methods of sample preparation
1. Wet ashing or acid digestion
2. Fusion
3. Pressure dissolution
4. Dry ashing
5. Microwave digestion
[For details- Refer a Research paper]
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13. Advantages of Atomic Absorption Spectroscopy
it is incredibly sensitive, measuring at parts per million (ppm).
It can analyse specific elements because of the unique light-absorbent qualities of their
atoms.
AAS can determine concentrations of over 65 elements.
It is a relatively simple process.
It is inexpensive in comparison to other analytical techniques.
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14. Applications-
Mining and Geology – The elemental composition of minerals and rocks provide
valuable information on the commercial feasibility of conducting mining activities in
areas explored. After mining, the ores and minerals need to be tested for composition
for the efficiency of refining operations. Similarly, trace metal analysis is of great
value in prospecting for oil and water deposits. With the help of AAS, the amount of
gold can be quantified to determine
Environmental Monitoring – Environmental monitoring for trace metal
contamination of industrial effluents, oceans, rivers and lakes is important for
establishing the safety of water for drinking and commercial use. It is important to
establish if such samples are within the safety limits set by regulatory bodies.
The analysis of drinking water is probably one of the most important applications of
AAS, especially in places where the environment is not properly cared for
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15. Materials Development – Common properties of materials such as hardness,
brittleness, grain size, crystallinity and amorphous nature are signifi cantly infl uenced
by composition and trace metals. Trace metal analysis can provide useful information
on the performance properties of such materials.
Pharmaceuticals – Trace metal analysis plays an important role in formulation
development, catalyst effi ciency and dosage limits. Most elements have a benefi cial
role up to certain prescribed limits but beyond such limits the effects are harmful.
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