UV/Vis Spectroscopy & Applications

UV/Vis Spectroscopy & Applications

• Ultraviolet/Visible (UV/Vis) spectroscopy is a technique used to measure the absorption of UV and visible light by a sample. It is a crucial technique in chemistry, biochemistry, and industry.
• Chromophores are molecules or ions that absorb light in the UV/Vis region, due to their electron configuration, enabling them to be analyzed using this technique.
• Key parameters in UV/Vis spectroscopy include:
  • Wavelength of measurement
  • Absorbance (A) or transmittance (%T) or reflectance (%R)
  • Changes in these parameters over time
• Four types of electronic transitions drive UV/Vis absorption in organic chromophores:
  • π–π*
  • n–π*
  • σ–σ*
  • n–σ*
• Transition metal complexes often exhibit color due to the presence of multiple electronic states associated with partially filled d orbitals.
• UV/Vis spectroscopy has applications in:
  • Monitoring structural changes in DNA
  • Quantitatively determining concentrations of diverse analytes, such as transition metal ions, organic compounds, and biological macromolecules
  • Analyzing solids, liquids, and gases
• The Beer–Lambert law states the absorbance of a solution is directly proportional to the concentration of the absorbing species and the path length of the light beam through the solution.
• UV/Vis spectrophotometers can be used as detectors for high-performance liquid chromatography (HPLC) to identify and quantify analytes.
• Wavelengths of absorption peaks can provide information about the types of bonds present in a molecule, aiding in the identification of functional groups.
• Woodward–Fieser rules are empirical observations that aid in predicting the wavelength of maximum absorption (λmax) for conjugated organic compounds.
• Factors that can affect the UV/Vis spectrum include:
  • Solvent
  • pH
  • Temperature
  • Electrolyte concentration
  • Interfering substances
  • Spectrophotometer slit width (effective bandwidth)
• Quantitative analysis using UV/Vis spectroscopy relies on the Beer-Lambert law:
  • A = εbc
    • A: Absorbance
    • ε: Molar absorptivity (extinction coefficient)
    • b: Path length
    • c: Concentration
• Molar absorptivity (ε) is a fundamental molecular property, specific to a particular substance, wavelength, solvent, temperature, and pressure.

This quiz explores the principles and applications of UV/Vis spectroscopy, a key technique in chemistry and biochemistry. It covers chromophores, electronic transitions, and the technique's usage in various scientific fields. Test your understanding of how UV/Vis spectroscopy is utilized across different applications.