Thin-Layer Chromatography - MCAT Chemical and Physical Foundations of Biological Systems

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Question

A new student is planning to use thin layer chromatography (TLC) for his research project. After setting up the apparatus the student forgets to place a lid on the TLC jar. He obtains poor results after running the TLC experiment. Which of the following can best explain his bad results?

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Answer

TLC is a laboratory technique commonly used to separate components of a mixture. Mixtures are placed on the TLC plate (stationary phase), which is then transferred to a jar containing the solvent. The solvent travels through the plate and carries components of the mixture along with it. Based on its properties, each component is dragged to different distances on the plate. The relative distances travelled by each component can be used for separation and identification.

It is important to place a lid on the jar because the solvent will be a volatile substance. An open system will allow for the solvent to evaporate from the TLC plate and reduce the amount of solvent travelling through the plate. The solvent in the solution will evaporate, but it is negligible and inconsequential to the data collected on the TLC plate.

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