3. INTRODUCTION
The electronic spectra ( Ultraviolet and
Visible ) of compound are associated with
measurement of energy absorbed when
electrons are promoted to higher energy
levels .
The wavelength range of UV at 2000-
4000 Å .
The range of UV – visible Spectra
4. HISTORY
“Ultraviolet” means “Beyond violet” ( from
Latin ultra “beyond” ) , violet being the colour
of the highest frequencies of visible light.
UV radiation discovered
in 1801 when the German
Physicist Johann Wilhelm
Ritter .
5. PRINCIPLE
UV absorption spectra arise from transition of
electron with in a molecule from a lower level to
high level .
A molecule absorb ultraviolet radiation of
frequency (ʋ) the electron in that molecule
undergo transition from lower to high energy level.
The energy can be calculated by :
Etotal = Eelectranic + Evibrational + Erotational
6. INSTRUMENTATION
A spectrophotometer is a
device which detects the percentage
transmittance of light radiation when
light of certain intensity and frequency
range is passed through the sample .
Thus, the instrument compress the
intensity of the light with that of the
incident light .
7.
8. BEER-LAMBERT LAW
According to the Beer-Lambert law the
absorbance is proportional to the concentration of
the substance in solution and as a result UV –
Visible spectroscopy can also be used to measure
the concentration of a sample .
The Beer - Lambert law can be expressed in from
of the following equation ;
A = εcl
Where;
A= Absorbance
l = Optical path length
c = Concentration of solution ( mol dm-3
)
ε = Molar extinction
9. APPLICATION
Ultraviolet Spectrophotometric methods find
extensive use in the identification of various hydrocarbons ,
vitamins, steroid, heterocyclic, and conjugated aliphatics.
Quantitative Analysis:-
UV absorption spectroscopy can
characterise those types of compound which
absorb UV Radiation. These compounds contain
either unbounded electron ( n – electron ) or the
conjugated double bond system ( π – electron ) such
as aromatic compound .
10. Identification of an Unknown Compound :-
An unknown compound
can be identified by comparing its spectrum with the
known spectra UV absorption method is less useful
then IR and NMR method .
Detection of Functional Group :-
UV technique is
applied to detect presence or absence of the
chromospheres .
11. CONCLUSION
We can conclude that UV
spectroscopy is best method which routinely
used in analytical chemistry for the
quantitative determination of different
analytes , such as transition metal ions, highly
conjugated organic compound and biological .
12. REFERENCE
“Spectroscopy” By :-
“H. Kaur”
(Page No. 314-315)
“Elementry Organic Chemistry” By :-
“Y. R. Sharma”
(Page No. 11-17)
