Absorption spectrophotometry vs. Ultraviolet-Visible Range Spectrophotometry


Spectrophotometry is a technique employed when quantitative measurement and analysis of specific spectra of light is required. From simple quality assurance techniques to advanced chemical analysis, spectrophotometry is a robust and widely used process that spans multiple disciplines and industries. Because there are many different types of light, and because the tools and techniques used to measure and quantify them are also different, there are specific tools that must be used depending on the type or spectrum of light that needs to be measured.

Spectrophotometry is a technique employed in many disciplines such as engineering, chemistry, and biology. It's used to quantify the reflective and transmissive properties of a material in terms of wavelengths of light that the material are exposed to. Because there are many types of light, such as visible and infra-red light, there are multiple types of spectrophotometry that each correspond to a specific regions of the light spectrum. As such, there are also different types of spectrophotometer, each with specific capabilities that provide for different uses and types of analysis. Among the different types of spectrophotometry, there are two primary methods employed; absorption spectrophotometry, which is concerned with the absorption of radiation and specific spectra of light, and Ultraviolet-Visible Range spectrophotometry, which is concerned with the reflectance of specific spectra of a given material. Each of these methods of analysis has specific uses, and also each have corresponding tools that are specific to that type of analysis.

Absorption Spectroscopy

Absorption spectroscopy is often used in chemical analysis, such as in protein assay analysis where visible ultra-violet light is tested against an aqueous solution to find the concentration of protein. It works because all proteins absorb light at specific wavelengths and, through the use of specific formulae, the amount of light which is absorbed can be calculated by detecting the amount of light which is reflected from the solution, thus allowing scientists to determine the amount of protein. In protein quantification, an absorption spectrophotometer produces light and then reduces it to a single wavelength using a component called a monochromator. The monochromatic light is set at a wavelength that is not absorbed by the container in which the sample is held because this would negatively impact the spectrophotometer's ability to measure reflectance.

Ultraviolet-Visible Range Spectrophotometry

Ultraviolet-Visible spectrophotometry is concerned with the visible spectra of light, and is used heavily in the ink, dye, and paint industries among many others. These industries, which rely heavily on specific and precise color data, make use of spectrophotometers and colorimetry science in order to produce subtle shades and color variations along wide ranges of colors. Because there are many factors that can influence the reflectance and transmission properties of a pigment, color data is routinely used to quantify and match the colors from sample materials in order to create custom paints and dyes. Similarly, UV/VIS spectrophotometers are helpful by many manufacturing companies as part of routine quality assurance practices because these devices can quantify deviance from an expected color, and can aid in diagnostics of equipment and manufacturing processes.

Regardless of the application, accurate spectrum quantification is an important part of many scientific tests. There are many methods to measure and to analyze the various regions of the spectrum, and each method has its own set of best practices and procedures and the key to any scientific experiment is to ensure that all control and documentation methods are followed so that results can be repeated by other scientists. Spectrophotometers are remarkable tools that are used in many labs from educational institutions to government organizations and crime labs.

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