UVVis spectroscopy

UV-Vis Spectroscopy

Electromagnetic radiation such as visible light is commonly treated as a wave phenomenon, characterized by a wavelength or frequency. Ultraviolet-visible spectroscopy(UV-Vis or UV/Vis) involves the spectroscopy of photons in the UV-visible region. This means it uses light in the visible, adjacent (near ultraviolet (UV) and near infrared (NIR)) ranges. The absorption in the visible ranges directly affects the color of the chemicals involved. In this region of the electromagnetic spectrum, molecules undergo electronic transitions. The Lambert-Beer law states that the absorbance of a solution is directly proportional to the concentration of the absorbing species in the solution and the path length. Thus, for a fixed path length, UV/VIS spectroscopy can be used to determine the concentration of the absorber in a solution.

The observed absorption bands are characteristic for extension of the pi-system in the molecule. As well delocalisation of the pi-electrons in the molecule as involved hetero atoms and groups lead to bands shifted to lower energy levels and signal broadening. Also interactions of the solute with the solvent leads to broadened signals.