Application of UV in Chemical Analysis
Application of UV in Chemical Analysis
Also called as Ultraviolet–visible spectroscopy, it is one of the methods of Instrumental analysis which is itself a part of analytical chemistry that investigates analytes using scientific instruments. For a better clarification, the keywords are further explained :
1. Instrumental Analysis: A part of analytical chemistry that investigates analytes using scientific instruments. It consists of process like Spectroscopy, Mass spectrometry,Crystallography,Electrochemical analysis, Calorimetry, etc
2. An analyte, or component is a substance or chemical constituent that is of interest in an analytical procedure.
3. Analytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials.While qualitative analysis gives an indication of the identity of the chemical species in the sample, quantitative analysis determines the amount of one or more of these components. The separation of components is often performed prior to analysis.
BLOCK DIAGRAM OF INSTRUMENTAL CHEMISTRY
UV Spectroscopy is defined as absorption spectroscopy or reflectance spectroscopy in the ultraviolet-visible spectral region. It utilizes light in the visible and adjacent (near-UV and near-infrared (NIR) 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, molecules undergo electronic transitions, from ground state to excited state.
Working Principle : Molecules with π-electrons or non-bonding electrons (n-electrons) absorb the energy in the form of ultraviolet or visible light to excite these electrons to higher anti-bonding molecular orbitals.But the resulting structures are unstable and the electrons fall back to their ground state, releasing the extra energy absorbed in the form of radiations.
APPLICATIONS OF UV SPECTROSCOPY
1. Detection of Impurities
UV absorption spectroscopy is one 
of the best methods employed for determination of impurities in organic molecules. Additional peaks are 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.
2. Structure elucidation of organic compounds.
UV spectroscopy is useful in the structure elucidation of organic molecules, the presence or absence of unsaturation, the presence of hetero atoms. From the location of peaks and combination of peaks, it can be concluded that whether the compound is saturated or unsaturated, hetero atoms are present or not etc.
3. Quantitative analysis
Also used for the quantitative determination of compounds that absorb UV radiation. This determination is based on Beer’s law which is as follows.
A = log I0 / It = log 1/ T = – log T = abc = εbc
Where ε is extinction co-efficient, c is concentration, and b is the length of the cell that is used in UV spectrophotometer.
4. Qualitative analysis
UV absorption spectroscopy can characterize those types of compounds which absorbs UV radiation. Identification is done by comparing the absorption spectrum with the spectra of known compounds. It is generally used for characterizing aromatic compounds and aromatic olefins.
5. It is also used to study the kinetics of the reaction by passing UV radiation through the reaction cell and observing the absorbance changes.
6. To identify the presence or absence of a functional group in a compound.
Some Related Questions
Q1. What is UV?
Ans. Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, that is, in the range between 400 nm and 10 nm. It is so named as it lies just next to the visible spectra of violet color but remains invisible to the human eye.
Q2. What is UV Spectroscopy?
Ans. UV Spectroscopy is defined as absorption spectroscopy or reflectance spectroscopy in the ultraviolet-visible spectral region. It utilizes light in the visible and adjacent (near-UV and near-infrared (NIR) ranges. The absorption or reflectance in the visible range directly affects the perceived color of the chemicals involved.
Q3. What is Beer’s law ?
Ans. The law states that there is a logarithmic dependence between the transmission (or transmissivity),of light through a substance and the product of the absorption coefficient of the substance, and the distance the light travels through the material (i.e., the path length).
A = log I0 / It = log 1/ T = – log T = abc = εbc
Where ε is extinction co-efficient, c is concentration, and b is the length of the cell that is used in UV spectrophotometer.
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4 Responses to Application of UV in Chemical Analysis
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Ultraviolet spectroscopy has a wide range of applications on chemical analysis. Theoretical explanation of UV has been clearly described here. The author has also provided a block diagram which is really helpful for better understanding.
This article is helpful for chemistry interested students and gives the idea of usefulness of the UV rays.
the uv chemical analysis is quite informative article and provides the most needed information.
This article very clearly explains the uses of Ultraviolet Rays in chemical analysis.