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UV Visible Spectroscopy Handwritten Notes

Download free handwritten notes on UV Visible Spectroscopy covering topics like electronic transitions, chromophores, auxochromes, spectral shifts, solvent effects, Beer-Lambert's law, instrumentation, and applications.

Keywords:

• UV Visible spectroscopy PDF notes
• Instrumental Methods of Analysis notes
• BPharmacy Semester 7 handwritten notes
• Spectrophotometric titrations
• Beer-Lambert law derivation
• Chromophores and auxochromes

UV Visible Spectroscopy: A Comprehensive Guide

UV Visible spectroscopy is an instrumental technique used to study the interaction of ultraviolet (UV) or visible light with matter. It is widely employed in pharmaceuticals, chemistry, and biology to analyze compounds based on their absorption characteristics. Below is a detailed explanation of the key concepts covered in these handwritten notes.

1. Electronic Transitions

UV Visible spectroscopy primarily deals with electronic transitions within molecules. These transitions occur when electrons in a molecule absorb energy from UV or visible light and move to higher energy levels. Common types of electronic transitions include:

• σ → σ*: Occurs in saturated compounds.
• π → π*: Seen in unsaturated systems like alkenes and aromatic rings.
• n → π*: Involves non-bonding electrons, common in carbonyl compounds.

2. Chromophores and Auxochromes

A chromophore is a part of a molecule responsible for its color due to the presence of conjugated double bonds or other functional groups that absorb UV or visible light. Examples include carbonyl groups, nitro groups, and aromatic rings. An auxochrome is a substituent that enhances the intensity of absorption by extending conjugation or altering the electron distribution. Examples include hydroxyl (-OH), amino (-NH2), and halogen groups.

3. Spectral Shifts and Solvent Effects

The position and intensity of absorption peaks can be influenced by solvents. Polar solvents often cause bathochromic (red) shifts, where the absorption maximum moves to longer wavelengths. Non-polar solvents may result in hypsochromic (blue) shifts, shifting the absorption to shorter wavelengths.

4. Beer-Lambert Law

The Beer-Lambert law states that the absorbance of a solution is directly proportional to its concentration and path length:

A = εcl

• A: Absorbance (unitless)
• ε: Molar absorptivity (L mol⁻¹ cm⁻¹)
• c: Concentration (mol L⁻¹)
• l: Path length (cm)

Deviations from this law can occur due to high concentrations, stray light, or chemical interactions.

5. Instrumentation

The components of a UV Visible spectrophotometer include:

• Sources of Radiation: Tungsten lamps for visible light and deuterium lamps for UV light.
• Wavelength Selectors: Monochromators or filters to isolate specific wavelengths.
• Sample Cells: Quartz or glass cuvettes for holding samples.
• Detectors: Phototubes, photomultiplier tubes, photovoltaic cells, or silicon photodiodes to detect transmitted light.

6. Applications

UV Visible spectroscopy finds applications in:

• Spectrophotometric Titrations: Determining the endpoint of reactions using absorbance changes.
• Single Component Analysis: Quantitative determination of a single analyte in a sample.
• Multi-Component Analysis: Simultaneous analysis of multiple components in complex mixtures.

These handwritten notes provide a comprehensive overview of UV Visible spectroscopy, making them ideal for BPharmacy Semester 7 students studying Instrumental Methods of Analysis.

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