here we can get information about electromgnetic radiation, colorimetry and ultraviolet visible spectroscopy

1. UV-Vis Spectroscopy

2. EMR = Electromagnetic Radiations
Radio waves
Microwaves
Infrared radiation
Visible light
Ultraviolet radiation
X-rays
Gamma rays

3. EMR = Electromagnetic Radiations

4. EMR = Electromagnetic Radiations

5. WAVELENGTH

6. EMR AS PER WAVELENGTH & FREQUENCY

8. FREQUENCY

9. ULTRAVIOLET RADIATIONS WAVELENGTH (nm)

10. VISIBLE RADIATION WAVENLENGTH (nm)

11. UV-Vis Wavelengths

12. COLORIMETER USED TO ANALYZE
COLORED
SOLUTIONS

13. Dispersion of light

15. ABSORPTION & TRANSMISSION

18. COLORIMETER Vs UV-Vis Spectrophotometer
COLORIMETER - Only colored solutions can be
analyzed
UV-Vis spectroscopy - Both colored and
colorless solutions can be analyzed

21. ELECTRONIC TRANSITION
Electronic transitions take place when electrons
in a molecule are excited from one energy level to a
higher energy level.
The energy change provides information on the
structure of a molecule and determines many
molecular properties

22. HIGHER ENERGY LEVEL
OR
EXCITED STATE
LOWER ENERGY
LEVEL OR GROUND
STATE
ELECT
RONS

23. ELECTRONS INVOLVED IN ELECTRONIC
TRANSITION
1. Sigma electrons (Bonding electrons)
2. Pi electrons (Bonding electrons)
3. n electrons (Non bonding electrons)

27. CHROMOPHORES

31. BEER-LAMBERT’S LAW
Johann Heinrich Lambert
August Beer

32. The absorbance is inversely proportional to the transmittence of the
solution

33. BEER’S LAW
Absorbtion of radiation is directly
proportional to concentration of
solution
A α c …...Eqn. 1

34. LAMBERT’S LAW
Absorbtion of radiation is directly
proportional to path length of
solution
A α l …...Eqn. 2

35. DEFINITION
The Beer-Lambert law states that the
quantity of light absorbed by a
substance dissolved in a fully
transmitting solvent is directly
proportional to the concentration of the
substance and the path length of the
light through the solution.

36. From eqn. 1 & 2
A α cl
A = εcl

37. A = εcl
A = Absorbance
ε = Molar absorptivity or Molar extinction
coefficient or Molar absorption coefficient
C = Concentration
l = Path length (cm)

38. DERIVATION OF LAW
- A spectrophotometer is an apparatus that measures the intensity, energy
carried by the radiation per unit area per unit time, of the light entering a
sample solution and the light going out of a sample solution.
- The two intensities can be expressed as transmittance: the ratio of the
intensity of the exiting light to the entering light or percent transmittance
(%T).
- Different substances absorb different wavelengths of light. Therefore, the
wavelength of maximum absorption by a substance is one of the
characteristic properties of that material.
- A completely transparent substance will have It = I0 and its percent transmittance will
be 100.
- Similarly, a substance which allows no radiation of a particular wavelength to pass
through it will have It = 0, and a corresponding percent transmittance of 0.

39. Deviations to the law
The Beer-Lambert law maintains linearity under specific
conditions only.
The law will make inaccurate measurements at high
concentrations because the molecules of the analyte
exhibit stronger intermolecular and electrostatics
interactions which is due to the lesser amount of space
between molecules.
This can change the molar absorptivity of the analyte.

40. Applications
Generally, it can be used to
determine concentrations of a
particular substance, or determine the
molar absorptivity of a substance.

41. UV-Vis spectrophotometer
1. Single beam UV-Vis spectrophotometer
(only sample can be placed)
2. Double beam UV-Vis spectrophotometer
(Both sample & reference can be placed)

44. Sample e.g. height of the boy ??????????????

45. Reference e.g. boy of 6 feet

46. On comparing with reference sample’s information
can be obtained
REFERENCE SAMPLE
6 FEET 4 FEET

48. INSTRUMENTATION
1. Light source
2. Collimator
3. Monochromator
4. Slit (wavelength selector)
5. Sample holder / cuvette
6. Mirror (beam splitter, reflecting mirror & grid mirror)
7. Detector
8. Recorder

49. Light source
1. Halogen lamp
2. Deuterium lamp
3. Xenon lamp
4. Xenon flash lamp
5. Low pressure mercury lamp
Many spectrophotometers uses a halogen lamp for
the visible range and a deuterium lamp for the
ultraviolet range according to the wavelength
requirement.

50. Collimator
Also called collimating lens
A collimator is a device which narrows a beam of particles or
waves.
To narrow can mean either to cause the directions of motion to
become more aligned in a specific direction (i.e., make collimated
light or parallel rays)

51. Collimating lens

52. Monochromator
Converts polychromatic light to monochromatic light
of specific wavelength
Mono = single
Poly = many
Chrome = color

54. Slit - Allows a specific wavelength to pass through it

55. Sample holder / cuvette

57. Mirror
Beam splitter
Reflecting mirror
Grid mirror

60. GRID MIRROR
It collects all radiations and send in one direction

61. DETECTORS

67. Silicon Photodiode

71. RECORDER

73. GRAPH
GRAPH

74. APPLICATIONS

82. 6. Spectrophotometric
titrations

84. Spectrophometric titration -
During a spectrophotometric titration, we
monitor changes in absorbance to
determine the equivalence point.
The end point is where the graph is
discontineous.

85. SPECTROPHOTOMETRIC CURVES

86. 7. Single component &
multicomponent analysis

96. TAPAN KUMAR MAHATO
tapan.mahato@gmail.com