UV-Visible spectroscopy. introduction. study of radiations in the range of 200 nm-800nm. principle. instrumentation layout.

1. UV- VISIBLE
SPECTROSCOPY
Presented by,
Jikhila Machado
1st M. Pharm
Pharmaceutical Analysis

2. INTRODUCTION
■ UV – 200 nm to 400 nm
■ Visible – 400 nm to 800 nm
■ In these only the valence electrons will absorb the energy thereby
molecules undergo transition from ground state to excited state.

3. PRINCIPLE
■ When molecules absorb UV Or visible radiation the electrons get promoted
from ground state to excited state.
■ Any molecules with n, π Or σ Or combination of these electrons can be excited
by the absorption of UV radiation.
■ Types of electronic transitions ;
a) n –π*
b) π –π* n : non- bonding electron
c) n – σ* π ,σ: Bonding electrons
d) σ – σ*

5. 1) n –π*:
•Requirelowest energy
•Also called R- band
• An electronfrom now bondingorbital is promoted go anti-bondingπ* orbital
•compoundscontainingdoublebondsinvolving hetero atoms undergo these types of
transition.
2) π –π*:
•π electronin a bondingorbital is excited to correspondinganti-bondingorbital π*.
•energy requirement is less
• Give B, E, K bands

6. 3) n – σ*:
•Saturated compounds containing one heteroatom with unshared pair of
electrons like O, N, S are capable of this transition.
•require less energy
•called as end absorption. Usually occur from 180-250nm .
•Hypsochromic shift or Blue shift.
4) σ – σ* :
•Highest energy is required
•Here, σ electrons get excited to corresponding anti-bonding orbital σ*.
•Observed with saturated compounds.
• Less informative.

7. INSTRUMENTATION LAYOUT

8. REFERENCES
•Text book of pharmaceutical analysis, 5th edition by, Dr. S. Ravi sankar ,
page no;1.9 to 1.26,2.2 to 2.7
•Instrumental methods of chemical analysis by, Gurdeep. R. Chatwal, page
no;2.149-2.153
•Pharmaceutical analysis by, P. D. Chaithanya sudha, page no;188-190.

9. THANK YOU