Principle of UV-Visible Spectroscopy

Introduction

Principle of Spectroscopy is how the spectra can absorb UV light. The absorption of light refers to a vital chapter in chemistry. Absorption of ultraviolet radiation results in an excitation of the electrons available in the substances.

About Spectrophotometer

A spectrophotometer refers to a scientific instrument is primarily utilised for the analysis of electromagnetic radiation from the light to the sample and about its absorption wavelength. The absorption is measurement using the spectral components. The spectrophotometer is used to measure molecular spectroscopy. In physics, radiation is the emission or transmission of energy in the form of wavelength or particles. There is a source of radiation in spectrophotometer to analysis wavelength of sample properly.

Information about UV-Vis spectroscopy

The term UV-Vis refers to the UV visible spectroscopy, which is a technology to analyse and measure the quantity of discrete wavelengths of light absorbed by given sample. The source of wavelengths is from UV-visible light. The UV lights are transmitted to the blank sample. The spectrophotometer has the potential to measure actual quantity of the absorbed light. .

Light contains a specific amount of energy that is inversely proportional to its wavelength. Therefore, shorter wavelength refers to more amount of energy and vice versa. However, a specific amount of energy is required to promote electrons from lower stationary state to higher stationary state detected by spectrophotometer as absorption spectra.

Figure 1 − Example of absorption spectrum taken from a UV-Vis spectrophotometer

The occurrence of the light from different sources promotes electrons to the higher energy state. Moreover, the wavelength around 380 nm of light is visible to human eyes generates in the spectrum. Violet colour exerts with wavelength of 380 nm and the wavelength of 780 nm of light is responsible for red light. The application of the UV-Vis spectroscopy is for identification of actual quantity of analytes.

Principle of Spectroscopy

Spectroscopy is the technique depends on the interaction of the light and matter is studied. Spectroscopy is also known as the properties of light. The primary use of the spectrophotometer is to identify the presence of any particles able to absorb or emit light in solution state. Thus, the study is done by measuring absorbed and emitted electromagnetic radiation. The spectroscope is also considered as optical spectroscope. Generally, this technique is applied to study the wavelengths with the help of spectral lines to identify the light intensity.

Types of Spectroscopy

The followings are some of the most useful types of Spectroscopy −

• IR Spectroscopy − Infrared or IR spectroscopy is able to detect electromagnetic radiation lying in the regions of infrared spectrum of analyte. The spectroscopy undergoes absorption and emission of light. IR spectroscopy is used to study different chemical functional groups present in unknown molecules.

• UV Spectroscopy − The Ultraviolet or UV spectroscopy is also considered the absorption spectroscopy or the reflectance spectroscopy. It is useful to measure electromagnetic spectrum lies in the UV region. It is used in bacteria culture and identification of different types of drugs. It is used to check the purity of nucleic acid.

• Mass Spectroscopy − Mass Spectroscopy is studied to understand the protein- ligand interactions. It is used in the field of biomolecules. The analytical tool is used to measure mass-to-charge ratio of one or more molecules present in the sample. The deflection of an ion caused by the magnetic field is dependent on their masses.

UV-Visible Spectroscopy and the Beer-Lambert Law

The Beer-Lambert law states that the concentration and path length of the sample is directly proportional to the absorbance of the light. The sample solution absorbs energy within a specific range of the beam of monochromatic light. The beam of the light intensity rate can be by the probability of electronic transition. The relationship between the intensity and beam is in inversion rate.

The work process of UV-Vis spectrophotometer

The working process of a UV-Vis spectrophotometer depends on the following variables −

Figure 2 − Main components in a UV-Vis spectrophotometer

• Source of light − In this process, monochromatic light can emit in wide range of wavelength. Both UV and visible ranges of light are used in spectrophotometer. The Deuterium lamp is used to measure UV and tungsten lamp is used for visible range of light.

• Selection of Wavelength − The spectrophotometer detects the wavelengths due to absorption and emission of radiation by the given sample from the source of light.

Conclusion

The absorption of radiations excites the sample molecule at higher energy level, is detected by spectrophotometer as a result of absorption spectra. The analysis of the atomic mass of the sample molecule is accomplished using mass spectrophotometer. The broadband radiation is used in the spectrophotometer for analysis of the exact output in the form of spectroscope.

FAQs

1. Why is a glass cuvette not suitable for UV?

Most plastics and glass can absorb UV radiation and the quartz material based reusable cuvettes are used to measure the UV radiation.

2. What are the types of IR Spectroscopy?

IR Spectroscopy can be classified into three sections, namely − the near-infrared, mid- infrared, and far-infrared spectroscopy. The range between 13000-4000 cm-1 is for near- infrared, mid-infrared ranges from 4000-400 cm-1, and far-infrared ranges from 400-10 cm-1.

3. What is the use of a spectrophotometer?

The spectrophotometer is used in measuring the UV-Vis wavelengths of the analytes with the help of electromagnetic radiation. A spectrophotometer can absorb or transmit the source of light. The spectroscopic analysis of the analytes is another application of it.