pharmaceutical Analysis, spectroscopy, uv spectroscopy

1. UV SPECTROSCOPY
DEPT OF PHARMACEUTICAL ANALYSIS
SREE DATTHA INSTITUTE OF PHARMACY,
SHERIGUDA, IBRAHIMPATNAM,TELANGANA-501510
SUBMITTED BY
K.GOUTHAMI REDDY[B.PHARMACY 4TH YEAR]16U21R0002
UNDER THE GUIDANCE OF
ASST.PROFESSOR K.SADHANA REDDY MAM

2. CONTENTS:
• INTRODUCTION TO UV SPECTROSCOPY
• PRINCIPLE
• ELECTRONIC TRANSISTIONS
• INSTRUMENTATION
• TYPES OF INSTRUMENTS
• APPLICATIONS
SREE DATTHA INSTITUTE OF PHARMACY

3. INTRODUCTION TO UV SPECTROSCOPY :
• It is concerned with the study of absorption of UV radiation which ranges
from 200nm to 400nm .Compounds which are colorless absorb radiation in UV
region.
• In both UV as well as visible only valence electrons absorb energy ,thereby
molecule undergoes transition from ground state to excited state.
• This absorption depends upon concentration and pathlength as given by Beer-
lamberts law .
• Any molecule consists of sigma (saturated compounds), π(unsaturated
compounds) or n (non-bonding) electrons.
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4. PRINCIPLE :
• The bonding and nonbonding electrons or combination of these electrons present
in the molecule absorb the characteristic radiation and undergoes transition from
ground state to excited state .
• Based upon the characteristic absorption peaks the nature of electrons present and
hence the molecular structure can be elucidated .
SREE DATTHA INSTITUTE OF PHARMACY

5. ELECTRONIC TRANSISTIONS
• The various electronic transitions are n-->π*,π-->π*,n-->sigma* and sigma to
sigma*.
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6. INSTRUMENTATION:
• Source of light:
1. Hydrogen discharge lamp
2. Deuterium lamp
3. Xenon discharge lamp
4. Mercury arc
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7. MONOCHROMATORS:
• GRATINGS monochromators are used.
• Gratings are of two types- 1.Diffraction grating and 2. Transmission grating
• In diffraction grating diffraction produces reinforcement whereas in transmission
grating refraction produces reinforcement.
• Gratings are made up of quartz.
• Bandpass - 0.4 to 2nm.
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8. SAMPLE CELLS:
• Sample cells are made up of QUARTZ only since glass cells absorb UV
radiation.
• Pathlength of cells are 10mm or 1cm.
• Shape is cylindrical or rectangular.
• Sample volume is 0.5ml or less for small volume cells and 5-10ml for large
volume cells.
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9. SOLVENTS:
• Solvent plays an important role in UV spectra since compound peak could be
obscured by solvent peak.
• Common solvents used and absorption regions are:
• Water - 191nm
• Cyclohexane - 195nm
• Methanol - 203nm
• Ethanol - 204nm
• Ether - 215nm
SREE DATTHA INSTITUTE OF PHARMACY

10. DETECTORS:
• TYPES OF DETECTORS:
• Barrier layer cell or photo voltaic cell
• Photo tubes or photo emissive cells
• Photo multiplier tubes [PMT]
• Recorders are connected to the detectors which show the resultant absorbance
value
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11. PHOTO MULTIPLIER TUBE:
• Diagram:
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12. DOUBLE BEAM UV SPECTROPHOTOMETER:
• Radiation source [hydrogen discharge tube or deuterium lamp] +
monochromator[gratings] + Beam splitter
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13. APPLICATIONS:
QUALITATIVE ANALYSIS:
• A) Determination of purity
• B) Identification of the compound
QUANTITATIVE ANALYSIS
• A) Absorbance factor method - %purity =observed absorbance/A1cm1% ×100
• B) Reference standard method-% purity =observed absorbance/avg A1cm1%×100
• C) Direct comparison method- A std = €C std × t
• D) Calibration curve method
• E) Difference spectrophotometric method
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14. • Keto-enol tautomerism
• Cis- trans isomerism
• Conjugation
• Functional group determination
• Alkyl substitution
• Presence or absence of unsaturation
• Presence or absence of heteroatom
• Number of rings
• Identification of unknown compound
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15. • Structure of organic compounds
• Determination of molecular weight
• Determination of P ka value (dissociation constant) of acids and bases
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16. REFERENCE
INSTRUMENTAL METHODS OF CHEMICAL
ANALYSIS
SKOOG, CHATWAL, B. K SHARMA
SREE DATTHA INSTITUTE OF PHARMACY