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The Principle of Ultraviolet Spectrophotometer

August 27, 2020

Uv-vis spectroscopy is considered as an important tool in analytical chemistry.In fact, this is one of the most commonly used techniques in clinical and chemical laboratories.This tool is used for qualitative analysis and identification of chemical substances.However, its main use is in the quantitative determination of different organic and inorganic compounds in solution.

Spectroscopy is basically about the interaction between light and matter.As light is absorbed by matter, the result is an increase in the energy content of atoms or molecules.The absorption of the compound to visible or ultraviolet light produces a different spectrum.

When ultraviolet radiation is absorbed, this causes electrons to be excited from the ground state to the higher energy state.The theory surrounding this concept states that the energy of the absorbed ULTRAVIOLET radiation is actually equal to the energy difference between the high energy state and the ground state.

Ultraviolet Visible Spectrophotometer

Ultraviolet Visible Spectrophotometer

The basic principle of UV spectrum:

The principle of UV spectrophotometer conform to Beer-Lambert law.This law states that, whenever a monochromatic beam passes through a solution of an absorbent substance, the rate of decline in radiation intensity and the thickness of the absorbent solution are in fact proportional to the concentration of the solution and the incident radiation.

The law is expressed by the following equation:

A = log (I0 / I) = ECI

A stands for absorbance, I0 for the light intensity on the sample pool, L for the light intensity leaving the sample pool, C for the concentration of solute, L for the length of the sample pool, and E for the molar absorption rate.

According to Beer-Lambert's law, it has been determined that the greater the number of molecules capable of absorbing light at a particular wavelength, the more light will be absorbed.

Application of ULTRAVIOLET spectrum:

The concept and principle of Ultraviolet visible spectrophotometer have many applications.For example, this is used to detect functional groups.It can be used to detect the presence or absence of chromophore in complex compounds.

This can also be used to detect conjugates in polyene.As the double bond increases, the absorption radiates to longer wavelengths.In addition, UV spectrum can be used to identify unknown compounds.The spectra of the unknown compound will be compared with those of the reference compound.If the two spectra coincide, the unknown compound will be successfully identified.

Uv spectra can also help determine the configuration of geometric isomers.It has been determined that cis-alkenes are absorbed at different wavelengths than trans-alkenes.If an isomer has a non-coplanar structure, it can still be determined by ULTRAVIOLET spectroscopy.

Finally, the tool can determine the purity of the substance.To this end, the absorptivity of sample solution was compared with that of reference solution.Absorption strength can be used to calculate the purity of a substance.



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