UV-visible spectroscopy involves using electromagnetic radiation in the ultraviolet-visible spectral region to analyze chemical substances. It operates based on the principle that molecules absorb specific wavelengths of UV or visible light. The absorbed wavelengths are characteristic of a molecule's chemical structure. A spectrophotometer directs a beam of light through the sample solution and measures the light absorption. UV-visible spectroscopy is useful for identifying organic compounds, detecting impurities, and quantitative analysis according to Beer's law. It has advantages of simple instrumentation and applicability to many organic molecules, but limitations include spectral overlap from mixtures and dependence on solution conditions.

1. UV-VISIBLE SPECTROSCOPY
SUBMITTED BY: SUBMITTED TO:
UDAYPAL Dr.MUNISH SIR
CUHP20PLS30

2. WHAT IS SPECTROSCOPY…..?
• The study of interaction of electromegnetic radiation with
the matter of inerest
• Mainly by:
Absorption
Emission
Scattering
ELECTROMEGNETIC RADIATION:
a kind of radiation
including visible light, radio waves, gamma rays,
and X-rays, in which electric and magnetic fields
vary simultaneously.

3. Wavelength range of UV-VISIBLE Light:
Wavelength range of UV light— 180-350nm
Wavelength range of VISIBLE light– 350-800nm
Wavelength range of UV-VISIBLE light-- 180-800nm

4. PRINCIPLE:
• Beer’s law:
Absorbance of monochromatic light is
directly proportional to the concentration of
solution
Lambert’s law:
Absorbance of monochromatic
light is directly proportional to the pathlength of
solution Molar absorption
coefficient specific for
every solution and
wavelength
Beers-Lamberts law:

5. Types of Transitions
• In UV spectroscopy
molecule undergo
electronic transition
involving sigma, pi
and n electrons. So it
is also often called as
electronic
spectroscopy.
• Four types of
electronic transitions
are possible.

6. INSTRUMENTATION:
• Radiation source for UV region:- H discharge lamp,deuterium
lamps and xenon discharge lamp
• Both deuterium and hydrogen lamps emit radiation in the range
160- 375nm.
• For visible region :- Tungston filament lamp
• use for region 350-2000nm.

7. • Monochromater:
It is a device used to isolate the radiation of
the desired wavelength from wavelength of continous spectra
Essential elements of monochromater are:
1.Entrance slit
2.Prism
3. Exit slit
Beam splitter: -split monochromatic light
Blank sample:A blank is a sample that contains everything
except for the analyte of interest(solvent,buffer,water,etc)
Sample :filled in sample cuvette
Photodetector:
The photodiode converts light into electrical
signals and temporarily stores them.
Quartz prism used in uv- region
Glass prism used in visible
region spectrum

8. Working:-
• A double beam spectrophotometer utilizes
two beams of light: a reference beam and a
sampling beam that passes through the
sample. Double beam spectrophotometers
have two detectors that allow the two beams
to be measured at one time.
Load reference sample in reference cuvette and
sample in sample cuvette
Compare absorbance of sample and reference
Absorbance is directly proportional to density of
solution

9. Applications:
. Detection of impurities:
Additional peaks can be
observed due to impurities in the sample and it can
be compared with that of standard raw material.
Structural elucidation of organic molecules:-
UV spectroscopy is useful in the structure
elucidation of organic molecules, the presence or
absence of unsaturation, the presence of hetero
atoms. From the location of peaks and combination
of peaks, it can be concluded that whether the
compound is saturated or unsaturated, hetero
atoms are present or not.

10. • Quantitative analysis:-UV absorption spectroscopy
can be used for the quantitative determination of
compounds that absorb UV radiation. This
determination is based on Beer’s law
• Qualitative analysis :-. Identification is done by
comparing the absorption spectrum with the spectra
of known compounds. UV absorption spectroscopy is
generally used for characterizing aromatic
compounds and aromatic olefins
• Chemical kinetics:-Uses to determine amount of
product and substrate.

11. Advantages
• Simple and inexpensive
instrumentation
• Most organic molecules
absorb UV/Vis light
• Quantitative (Beer’s
law)
Disadvantages
• Mixtures of molecules
can be problem due to
overlap(hence requires
significant sample
preparation.
• Spectra are not highly
specific for particular
molecules.
• Absorption can be
dependent on solution
conditions.

12. THANK YOU