UV spectroscopy

Ultraviolet–visible spectroscopy (UV-Vis or UV/Vis) refers to absorption spectroscopy or reflectance spectroscopy in the ultraviolet-visible spectral region. This means it uses light in the visible and adjacent ranges. The absorption or reflectance in the visible range directly affects the perceived color of the chemicals involved. In this region of the electromagnetic spectrum, atoms and molecules undergo electronic transitions. UV/Vis spectroscopy is routinely used in analytical chemistry for the quantitative determination of different analytes, such as transition metal ions, highly conjugated organic compounds, and biological macromolecules.

Principles

The basic principle of UV-Vis spectroscopy involves the absorption of ultraviolet or visible light by electrons in a molecule, promoting them from their ground state to a higher energy level. The Beer-Lambert law is applied to quantify the absorption of light. This law states that the absorption of light by a medium is directly proportional to the concentration of the absorbing species in the solution and the path length of the light through the solution.

Instrumentation

A typical UV-Vis spectrophotometer consists of a light source, a monochromator or filter to isolate the desired wavelengths of light, a sample compartment, and a detector. The light source is usually a deuterium lamp for the ultraviolet region and a tungsten lamp for the visible region. The monochromator is used to disperse the light into its component wavelengths and select the desired wavelength range. The sample is placed in the sample compartment, and the transmitted or reflected light is measured by the detector.

Applications

UV-Vis spectroscopy has a wide range of applications in various fields such as:

• Chemical analysis: It is used to determine the concentration of a substance in a solution by measuring the absorbance at a specific wavelength.
• Biochemistry: It is used for the determination of protein concentration, as well as the study of protein-ligand interactions.
• Pharmaceuticals: In the pharmaceutical industry, it is used for drug testing and quality control.
• Environmental monitoring: It is used for the detection of water pollutants and the analysis of water quality.

Advantages and Limitations

One of the main advantages of UV-Vis spectroscopy is its simplicity and versatility. It can be used for both qualitative and quantitative analysis and is applicable to a wide range of samples. However, it has limitations, such as the need for the sample to be transparent in the region of interest and the potential for interference from other absorbing species in the sample.

See Also

• Spectrophotometry
• Molecular spectroscopy
• Absorption spectroscopy