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Dr Gihan Gawish
1-Atomic Absorption Spectroscopy
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Energy absorbed by the sample is used to assess its
characteristics.
In analytical chemistry, atomic absorption spectroscopy is
a technique for determining the concentration of a
particular metal element in a sample
Sometimes absorbed energy causes light to be released
from the sample, which may be measured by a technique
such as fluorescence spectroscopy.
Dr Gihan Gawish
Atomic Absorption Spectroscopy
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Dr Gihan Gawish
2- visible
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Many atoms emit or absorb visible light.
In order to obtain a fine line spectrum, the atoms must
be in a gas phase.
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This means that the substance has to be vaporized.
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The spectrum is studied in absorption or emission.
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Visible absorption spectroscopy is often combined with
UV absorption spectroscopy in UV/Vis spectroscopy.
Dr Gihan Gawish
3- UV
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All atoms absorb in the Ultraviolet (UV) region.
UV spectroscopy is also used in
Quantifying protein
DNA concentration
The ratio of protein to DNA concentration in a
solution.
Dr Gihan Gawish
3- UV
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Several amino acids usually found in protein, such as
tryptophan, absorbs light in the 280nm range and
DNA absorbs light in the 260nm range.
For this reason, the ratio of 260/280nm absorbance
is a good general indicator of the relative purity of
a solution in terms of these two macromolecules.
Dr Gihan Gawish
4- Infrared
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It offers the possibility to measure different types of
inter atomic bond vibrations at different frequencies.
Especially in organic chemistry the analysis of IR
absorption spectra shows what type of bonds are
present in the sample.
Dr Gihan Gawish
5- Fluorescence
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It uses higher energy photons to excite a
sample, which will then emit lower energy
photons.
This technique has become popular for its
biochemical and medical applications, and can
be used for
confocal microscopy,
fluorescence resonance energy transfer,
and fluorescence lifetime imaging.
Dr Gihan Gawish
6- Raman
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When a beam of light passes through a sample, a small
fraction of the light exits the sample at a different angle.
If the wavelength of the scattered light is different than
the original wavelength, it is called Raman scattering.
Raman scattering of light by molecules may be
used to provide information on:
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a sample's chemical composition
2.
molecular structure
Dr Gihan Gawish
6- Laser
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Absorption
spectroscopy,
fluorescence
spectroscopy, Raman spectroscopy, commonly use
laser light as an energy source.
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Laser spectroscopies provide information about the
interaction of coherent light with matter.
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Laser spectroscopy generally has high resolution
and sensitivity.
Dr Gihan Gawish
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Dr Gihan Gawish
Electromagnetic (EM) radiation
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(EM) radiation is a self-propagating wave in space
or through matter.
EM radiation has an electric and magnetic field
component which oscillate in phase perpendicular to
each other and to the direction of energy
propagation.
Dr Gihan Gawish
Source of energy depending on electromagnetic
radiation
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Electromagnetic radiation is classified into types
according to the frequency of the wave, these
types include (in order of increasing frequency):
radio waves, microwaves, infrared radiation, visible
light, ultraviolet radiation, X-rays and gamma rays.
Dr Gihan Gawish
The Visible Spectrum
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The visible spectrum (or sometimes called the optical
spectrum) is the portion of the electromagnetic
spectrum that is visible to (can be detected by) the
human eye.
Electromagnetic radiation in this range of wavelengths
is called visible light or simply light.
A typical human eye will respond to wavelengths in
air from about 380 to 750 nm.
Dr Gihan Gawish