The document presents an overview of spectroscopy, focusing on UV and visible spectroscopy, its principles, and laws such as Beer’s and Lambert’s. It explains the processes of light absorption and electronic transitions of molecules that lead to qualitative and quantitative analysis. Additionally, it discusses the significance of chromophores and auxochromes in determining colors of compounds and the importance of solvent choice in spectroscopy.

1. Presented by,
Venkatesan R
M.Pharm 1st year
Department of pharmaceutical analysis
karnataka college of pharmacy
Presented to,
T. Sreenivas Rao sir
Assistant Professor
Department of pharmaceutical chemistry
karnataka college of pharmcy

2. Content
01
02
03
05
Introduction
Theory / Principle
Laws
Choice of solvent and solvent
effect
Chromophores / Auxachromes
04

3. 01. Spectroscopy
Spectroscopy divided into two types words
•To determine
scopy
•Light energy
•EMR (Electro Magnetic Radiation)
spectrum
Light energy is used to
determine the sample is
known as spectroscopy.
Uv and
visible
radiation
Microwaves
IR
Radiation
Gama ray,
X-ray
Radiowave
& cosmic
rays
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4. Spectroscopy
40% 50%
60%
80%
Spectroscopy is the branch of science which is used for quantitative analysis of
sample or matter by using (EMR) electromagnetic radiation
Spectroscopy is the measurement and interpretation of EMR absorbed or
emitted. Then the molecule are atoms of sample moves from one energy state
to another energy state.
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5. •Wavelength is the distance between
two successive maxima or minima
•It can be measured in meters (m),
centimeters (cm), millimeters (mm),
nanometres (nm)
wavelength
•Number of waves per
centimeters is known as wave
number.
•Wave number is expressed in
cm-1
wave number
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6. •Electromagnetic radiation
It’s a combination of electric and
magnetic radiation
Light flow in the form of wave which
contain photon (means packet of energy)
The electric and magnetic radiation
produces the transition
•Frequency
Frequency is the number of complete
wavelength units passing through a given
point in unit time.
Frequency is measured in Hertz (Hz),
cycles per second (CPS).
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7. Uv- visible spectroscopy
• Used for quantitative analysis of matter or sample by using
uv (ultra-violet) and visible light.
• The overall range of wavelength of uv and visible is 200 to
800 nm.
1.Uv range 200-400 nm
2.Visible range 400 – 800 nm
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8. Theory / Principle
• EMR light contain packets of energy now, when this light passes
through the sample.
• A particles or molecules of sample absorb this light so, particle get
excited.
• Now uv visible spectroscopy principle depends upon the absorption
of light.
• So, if we determine the intensity of light, then we calculate the
concentration of particle.
Absorption α concentration of particles.
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9. Beer’s and Lambert’s laws
According to this law,
light absorption is directly proportional to the
concentration and path length of solution.
• Principle of uv visible spectroscopy is based on beer’s
– lambert’s law.
Incident light
(Io)
Transmitted
light (I)
A = Σct
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10. • Electronic Transition
n – σ *
π – π *
n - π *
Divided into four types of
transition
σ – σ*
•The process or period of changing from
one state or condition to another.
•The electron transition is term of the
there are several possible electronic
transition that are occurs, each of a
different relative energy.
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11. Types of electronic transition
1. σ to σ* - transition of electron from sigma bonding orbitals to anti
bonding orbitals , higher energy required, shorter the wavelength.
Ex : Methane, Ethane
2. π to π* - π electron is a bonding orbital excited to π* anti
bonding orbitals, it contain unsaturated double or trible bond
Ex : Alkenes, Alkynes.
3. n to σ* - it involves saturated compound with atoms containing
lone pair of electrons.
Ex : O, N, S
4.n to π* - it require lowest energy than all transition so, wavelength
is higher, it observed double or triple bond
Ex : Aldehyde, Ketone
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12. Electric Transition
Electric Transition
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13. Chromophores
• Chromophore is molecule or part of molecule which having a
unsaturated double bond.
• So, it absorb light in Uv visible region and responsible for
importing colour to the compound.
• Two types of chromophore is there.
Indepent
chromophore
Dependent
chromophore
single chromophore
group imparts
colour to the
compound
more than one
chromophore is
required to produce
colour.
Ex : Acetone
Ex : Nitro
compounds
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14. Auxachromes
It is a group of atom that get attached to the chromospheres and
the colourfulness of the chromospheres also called in
enhancing groups.
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15. Choice of solvent and solvent effect
The choice of solvent used in uv spectroscopy is most
important because solvent can change the absorption curve.
A most suitable solvent is one that does not itself absorbs
radiation in the region under investigation (uv – visible).
spectroscopy).
Polarity decreases Absorption maximum wavelength increases
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16. References
• Pharmaceutical analysis – Ravishankar
• Modern Pharmaceutical analysis –
Dr.Shashikant D.Barhate.
• Pharmaceutical Chemical analysis - Austhoskar
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17. THANK YOU