UV / VISIBLE SPECTROSCOPY- Introduction ,Principles ,laws ,Instrumentation ,Applications

1. PRESENTED BY
Mr. Suraj J. Patil.
B Pharm.
UV / VISIBLE
SPECTROSCOPY

2.  Introduction
 Principles
 laws
 Instrumentation
 Applications

3. Spectroscopy
 It is the branch of science that deals with the
study of interaction of matter with light.
OR
 It is the branch of science that deals with the
study of interaction of electromagnetic
radiation with matter.

4.  Interaction of Radiation with a sample
 The study of molecular or atomic structure
of a substance by observation of its interaction
with electromagnetic radiation
 QUANTITATIVELY - For determining the
amount of material in a sample
 QUALITATIVELY – For identifying the
chemical structure of a sample

5. Electromagnetic Radiation
 Electromagnetic radiation consist of discrete
packages of energy which are called as
photons.
 A photon consists of an oscillating electric
field (E) & an oscillating magnetic field (M)
which are perpendicular to each other

7.  Electromagnetic Radiation
 Frequency (ν):
– It is defined as the number of times electrical
field radiation oscillates in one second.
– The unit for frequency is Hertz (Hz).
1 Hz = 1 cycle per second
 Wavelength (λ):
– It is the distance between two nearest
parts of the wave in the same phase i.e. distance
between two nearest crest or troughs.

8. Radiation Energy
• The strength of the radiation energy will interect with the
molecules in different ways:
– High energy sources produce breaking of bonds
X-Ray, γ Rays
– Medium energy sources excite electrons
UV / VISIBLE Spectroscopy
– Low energy sources produce vibrations in chemical bonds
Infrared Energy
– Very low energy sources produce rotation of the chemical bonds
Microwaves and Radio waves

9. Principles of Spectroscopy
• The principle is based on the measurement of
spectrum of a sample containing atoms
/molecules.
• Spectrum is a graph of intensity of absorbed or
emitted radiation by sample verses frequency(ν)
or wavelength (λ).
• Spectrometer is an instrument design to measure
the spectrum of a compound.

10. Principle
• The UV radiation region extends from 10 nm to 400 nm
and the visible radiation region extends from 400 nm to
800 nm.
Near UV Region: 200 nm to 400 nm
Far UV Region: below 200 nm
• Far UV spectroscopy is studied under vacuum
condition.
• The common solvent used for preparing sample to be
analyzed is either ethyl alcohol or hexane.

11. THE LAWS OF SPECTROPHOTOMETRY
There are two very important basic laws and a third
one which is a
combination of the two.
LAMBERTS LAW – ABSORBANCE (A) proportional to
the PATHLENGTH (l) of the absorbing medium.
BEERS LAW - ABSORBANCE (A) proportional to the
CONCENTRATION (c) of the sample.
BEER- LAMBERT LAW - ABSORBANCE (A)
proportional to c x l
A ∞ cl
A = Ecl (A is a ratio and therefore has no units)
The constant E is called the MOLAR EXTINCTION
COEFFICIENT

12. The possible electronic transitions can graphically
shown as:

13.  Instrumentation

14. Parts of instrumentation
1. Source
2. Entrance slit
3. Dispersion device
4. Exit slit
5. Sample
6. Detector

15. • Qualitative analysis
• Quantitative analysis
• Detection of functional groups
• Detection of extent of conjugation
• Identification of an unknown compound
• Determination of configuration of geometrical
isomers
• Determination of purity of substance