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  • Applications of Absorption Spectroscopy (UV, Visible)

    1. Detection of Impurities
    UV absorption spectroscopy is one of the best methods for determination of impurities in organic molecules. Additional peaks can be observed due to impurities in the sample and it can be compared with that of standard raw material. By also measuring the absorbance at specific wavelength, the impurities can be detected.
    Benzene appears as a common impurity in cyclohexane. Its presence can be easily detected by its absorption at 255 nm.

  • Beer's and Lambert's Law

    When a light passes through absorbing medium at right angle to the plane of surface or the medium or the solution, the rate of decrease in the intensity of the transmitted light decreases exponentially as the thickness of the medium increases arithmetically.

    Accordingly, Lambert’s law can be stated as follows:

  • Elecromagnetic Spectra, EMR

    The entire range over which the electromagnetic radiation exists is known as electromagnetic spectrum.

  • Instrumentation of UV or Visible Spectroscopy


    Instruments for measuring the absorption of U.V. or visible radiation are made up of the following components;
    1. Sources (UV and visible)
    2. filter or monochromator
    3. Sample containers or sample cells
    4. Detector

    1. Radiation source
    It is important that the power of the radiation source does not change abruptly over its wavelength range.

  • Solvent effect on absorption spectroscopy and Difference between UV and Visible Spectroscopy

    Solvent Effect
    Solvents play an important role in UV spectra. Compound peak could be obscured by the solvent peak. So a most suitable solvent is one that does not itself get absorbed in the region under investigation. A solvent should be transparent in a particular region. A dilute solution of sample is always prepared for analysis. Most commonly used solvents are as follows.

  • Electronic transition level

    It was earlier stated that σ, π, and n electrons are present in molecule and can be excited from the ground state to excited state by the absorption of UV radiation. The various transitions are n→∏*, ∏→∏*, n→σ*, & σ →σ*

  • Analytical Aspects of Absorption Spectroscopy, (UV and Visible Spectroscopy)

    The word spectroscopy is derived from spectrum which means a bend of different colours formed due to difference in wavelength and skopin means examination or evaluation.

    Thus, spectroscopy is the branch of science that deals with the examination or evaluation of spectrum.

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