Editorial Feature

What is the Difference Between Spectroscopy and Spectrophotometry?

Analytical techniques are fundamental in advancing scientific knowledge, providing detailed insights into the composition and properties of materials. Among these techniques, spectroscopy and spectrophotometry stand out as essential methods.

What Is the Difference Between Spectroscopy and Spectrophotometry?

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Spectrophotometry, an experimental technique within the broader spectroscopy field, focuses on studying light-matter interactions. While the terms spectroscopy and spectrophotometry are sometimes used interchangeably, this article aims to differentiate the two.

Understanding Spectroscopy

Definition and Principles

Spectroscopy involves measuring light that has interacted with matter to understand the properties of both light and matter.1 This interaction can involve solids, liquids, gases, or even ultracold states of matter near absolute zero, such as Bose-Einstein Condensates (BEC).

The light source for spectroscopy can range from sunlight to specialized lasers, covering the entire electromagnetic spectrum. The information extracted from the interaction depends on the application's objective.

Types of Spectroscopy and Applications

Several fundamental occurrences in nature have been harnessed into experimental techniques for spectroscopy, including:

  • Absorbance: Using a spectrometer to measure a sample's light absorption as a function of wavelength. This method is commonly used to maintain the concentrations of absorbing species in solutions and is employed by biologists and biochemists to measure cellular components and functional molecules.2
  • Reflection: Measuring reflected or scattered light as a function of wavelength. Some photons are absorbed, passing through the sample, while others are reflected. Identifying and quantifying these photons provides valuable information.3
  • Transmission: Closely related to absorption spectroscopy, this method contrasts light that has traveled through a sample with light that has not. The final spectrum reveals details about the sample's absorption coefficient, reflectivity, angle of incidence, polarization, and particulate size and orientation.
  • Fluorescence: Measuring the intensity of photons emitted from a sample after it has absorbed incident photons. This method's sensitivity and selectivity make it valuable for studying real-time structures and dynamics of biomolecular systems under microscopes and in solution states.
  • Raman: Using scattered light to quantify a sample's vibrational energy modes. Raman spectroscopy provides structural and chemical information by analyzing a sample's unique Raman "fingerprint."4

These methods have evolved to address specific applications across various industries, including semiconductor, pharmaceutical, environmental, and oil and gas sectors. Consequently, the global market for spectroscopic components is estimated to exceed 50 billion USD in the next decade.

Understanding Spectrophotometry

Definition and Principles

Spectrophotometry is a specific category within spectroscopy focused on absorption spectroscopy to measure the constituents of a solution.

This technique measures light intensity as it passes through a sample solution to determine how much a chemical compound absorbs light.5 Each substance either transmits or absorbs light within a specific wavelength range, allowing for the quantification of known compounds.

Applications of Spectrophotometry

Spectrophotometry is a valuable quantitative analysis technique in fields such as chemistry, physics, biochemistry, material and chemical engineering, and therapeutic applications.

For example, precise optical property measurements are crucial for regulating the dosage and purity of drugs during product development, manufacturing, and quality control. Spectrophotometric techniques are essential in this process, ensuring compliance and assessing risks.6

Other applications include monitoring chemical concentrations in drugs and vaccines, water purification, and oil in gas analyzers.

Future Outlook

In summary, spectroscopy encompasses the general study of light-matter interaction, while spectrophotometry is a specific technique measuring light intensity for quantitative analysis.

Both fields are continuously evolving with advancements in optics and computing, allowing for increasingly detailed imaging and study of matter, thereby enhancing spectroscopy's profound impact on everyday life.

More from AZoOptics: Advances in Photonic Devices for Optical Computing

References and Further Reading

  1. Phillips, K. (2024) Spectrophotometry vs. Spectroscopy. [Online] Hunter Lab. Available at: https://www.hunterlab.com/blog/spectrophotometry-vs-spectroscopy/#:~:text=Spectroscopy%20is%20a%20study%2C%20while,absorption%20in%20a%20chemical%20substance.&text=Unlike%20spectrophotometry%2C%20spectroscopy%20alone%20doesn't%20produce%20results.
  2. Nilapwar, SM., Nardelli, M., Westerhoff, HV., Verma, M. (2011). Absorption spectroscopy. Methods Enzymol. doi.org10.1016/B978-0-12-385118-5.00004-9
  3. Andor. (no date). Absorption / Transmission / Reflection Spectroscopy. [Online] Andor. Available at: https://www.photonics.com/images/Web/WhitePapers/532/Andor_Learning_Absorption_Transmission_Reflection_Spectroscopy_For_Photonics.pdf
  4. Heller, EJ., Sundberg, R., Tannor, D. (1982) Simple aspects of Raman scattering. J. Phys.Chem. doi.org/10.1021/j100207a018
  5. LibreTexts. (no date) Spectrophotometry. [Online] LibreTexts. Available at: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/02%3A_Reaction_Rates/2.01%3A_Experimental_Determination_of_Kinetics/2.1.05%3A_Spectrophotometry
  6. Hammond, JP. (2014). The Use of Spectrophotometry in the Pharmaceutical Industry. Experimental Methods in the Physical Sciences. doi.org/10.1016/B978-0-12-386022-4.00011-X.

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Written by

Ilamaran Sivarajah

Ilamaran Sivarajah is an experimental atomic/molecular/optical physicist by training who works at the interface of quantum technology and business development.


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