Chromatography vs. Spectroscopy: What’s the difference?

Chromatography and spectroscopy are powerful analytical techniques used to identify the identity and quantity of different chemicals in solution. While they have similarities, their methods are fundamentally different. In this article, we’ll compare chromatography and spectroscopy on three levels—practicality, ease of use, and cost—to show you the difference between these two similar yet distinct analytical methods. We’ll also give you an example of how each technique can be used to answer different scientific questions!

Main Difference

Chromatography and spectroscopy are both analytical techniques used to measure the properties of molecules. Chromatography separates molecules based on their physical properties, such as size or polarity. Spectroscopy measures the electronic properties of molecules, including their absorption and emission spectra.

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Despite their similarities, chromatography, and spectroscopy are used for different purposes. Chromatography can be used to identify unknown compounds, while spectroscopy can be used to determine the structure of a molecule. Spectroscopy is also better at detecting small changes in the electronic properties of a molecule, which can be important for understanding chemical reactions.

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What is Chromatography?

Chromatography is the separation of components based on their physical and chemical properties. To separate the different components, they must be dissolved in some solvent. Once the solution is prepared, it is then injected into a column containing a stationary phase (a material that separates the solutes).

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As the sample passes through the column, the different components will bind to the stationary phase at different rates. When the sample reaches the end of the column, the other bound components will elute out of the column at different times. These fractions are collected and analyzed using various techniques.

What is Spectroscopy?

Spectroscopy is the study of electromagnetic radiation. Different substances emit or absorb specific frequencies of light. By measuring the frequency of these emissions or absorptions, scientists can determine what chemicals are in the sample.

There are many types of spectroscopy, including infrared, ultraviolet-visible, X-ray, nuclear magnetic resonance, Raman, and fluorescence. Each technique has its strengths and weaknesses.

Difference Between Chromatography and Spectroscopy

In a nutshell, chromatography separates a mixture distribution of the components between two phases. At the same time, spectroscopy is the identification and quantification of molecules by absorption or emission of electromagnetic radiation.
One key difference is that chromatography separates compounds based on their affinity for two different phases, whereas spectroscopy separates compounds based on their ability to absorb or emit light.
Another key difference is that in spectroscopy, no distinct physical boundaries separate the various substances, but in chromatography, distinct boundaries separate the different substances. It is also worth noting that when measuring concentration with chromatography, the volume measured is often challenging to discern (since this measurement is usually done via UV light).

  • Both Chromatography and Spectroscopy are analytical techniques utilized in chemical engineering.
  • They are also sometimes used in other fields such as biochemistry and forensic science.
  • They share some common elements, but they are fundamentally different techniques.
  • The sample is separated into components using a mobile phase and a stationary phase in chromatography.
  • The sample is placed in the stationary phase.
  • Each component interacts differently with the mobile phase, which allows it to separate.
  • In spectroscopy, light waves detect the presence of one or more compounds in a solution.
  • Electromagnetic radiation is passed through a sample solution.
  • The wavelengths that pass through undisturbed provide a signature of the compounds present in the sample solution.
  • These signatures can be compared against known reference signatures to determine which compounds are present.
  • Although both chromatography and spectroscopy are used in chemical engineering, they use different methods to get the same result.

Applications of Each Analysis Method

Both chromatography and spectroscopy are important analytical methods used in chemistry. They both have their unique applications and advantages. Chromatography is often used to separate and analyze compounds, while spectroscopy identifies and determines their structure. Some specific examples of chromatography applications include gas or liquid chromatography, which separates compounds based on weight and size differences. Gas chromatography helps decide what elements are present in a sample because it can identify whether there are lighter or heavier molecules present; this technique also helps determine if there are different types of atoms present like oxygen, nitrogen, hydrogen, carbon, or sulfur.

Limitations of Both Methods

While chromatography and spectroscopy are powerful analytical tools, they each have limitations. For example, chromatography can only be used to measure compounds capable of being dissolved in a solvent. In contrast, spectroscopy can be used to measure both soluble and insoluble compounds. Additionally, chromatography is limited to measuring compounds that interact with the column material, while spectroscopy can measure all compounds regardless of their interaction with the column material.

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Comparison Chart Between Chromatography and Spectroscopy

Chromatography

English
Noun
  • Any technique for separating components that are common to various mixtures of chemical substances, characterized by the systematic use of a mobile phase (liquid, gas) moving relative to a stationary phase (solid, liquid) – the differential rates of migration of the components between the two phases determines the separation.
Derived terms
GLC (high-performance liquid chromatography) – HPLC (ion exchange chromatography) – ZEISS paper chromatography – TLC (thin layer chromatography) are all different forms of gas chromatography.
Spectroscopy

English
Noun
  • (uncountable) The scientific study of spectra.
  • (analytical chemistry, countable) The use of spectrometers in chemical analysis.

Derived terms

  • spectroscopist

Conclusion

In conclusion, chromatography and spectroscopy are critical analytical techniques for identifying and quantifying compounds. While they both have their unique benefits, chromatography is generally better suited for separating compounds, while spectroscopy is better for identifying them.