Ultraviolet (UV)-Visible Spectroscopy

Ultraviolet (UV)-Visible Spectroscopy

UV-visible spectroscopy is a quantitative optical technique to determine the chemical composition of liquids and solids based on their optical properties (transmittance, reflectance, and absorbance). It is used to classify substances during research, production, and quality control in various industries. UV-vis spectroscopy is used to gain qualitative and quantitative information about a sample. It is routinely used to characterize a range of samples, including semiconductor materials, dyes, pigments, biological materials, transition metals, organic compounds, and many other manufacturing materials. Spectrophotometers that can perform micro-volume measurements are available for testing of small volume samples.

When a light beam comes in contact with a solid sample, it may be reflected, transmitted, or absorbed. The electrons in the liquid sample get excited after absorbing some of the light from the optical source. The intensity of light absorbed is directly related to the concentration of a molecule in the liquid sample. The absorbance spectrum of a sample can be compared to the available standards to identify and quantify a compound.

A UV/Vis spectrophotometer is the tool used in ultraviolet-visible spectroscopy. It determines the light’s intensity after passing through a sample (I), and compares it with the light’s intensity before passing through the sample (I_o). The ratio of I and I_o is called transmittance (T) which is expressed as a percentage. The Absorbance (A) is calculated as below:

A= -log(%T/100%)

This methodology is frequently employed in a variety of practical and theoretical applications since it is reasonably affordable and simple to execute. The sample must only be a chromophore and absorb in the UV-Visible range. Aside from the measurement wavelength, variables of importance include absorbance (A), transmittance (%T), and reflectance (%R), as well as how they change over time.

Video 01: Working of a UV-Visible Spectrophotometer

Ultraviolet (UV)-Visible Spectroscopy Common Uses

• Quantification of the bacterial cells in a cell culture
• Study of conformational changes (such as partial unfolding) in proteins
• Characterization of solid nano-bio materials that are homogeneously dispersed in a solvent
• Calculation of reaction kinetics by measuring the variation of the concentration of the compounds throughout the reaction
• Determination of the iron(III) concentration in wastewater
• Elemental analysis of astronomical objects

Advantages

• Easy to use and maintain
• A cost-effective technique to analyze the sample
• High sampling speed
• A non-invasive technique that keeps the integrity of the sample

Limitations

• Light sources in the deep UV range (100–200 nm) are expensive, so most spectrophotometers do not operate in this range
• Results can be influenced by sample conditions like pH, temperature, impurities, and contaminants
• It doesn’t work well for the samples in which solid particles are suspended in the liquid because such samples scatter light more than they absorb
• The material of the sample holder should have no absorption at the measurement wavelength

Industries

• Microbiology
• Food & Agriculture
• Material Science
• Optical Components
• Pharmaceutical Research
• Cosmetic Industry
• Quality Control

Ultraviolet (UV)-Visible Spectroscopy Laboratories

• Dynalene Labs
• ATS Applied Technical Services
• EAG Laboratories
• Smithers
• Pacific Bio Labs
• Arizona State University

More Details

• Working principle of UV-visible Spectroscopy
• Limitations of UV-visible Spectroscopy
• Advantages and uses of UV-visible Spectroscopy