Thin-Layer Chromatography (TLC) Flashcards

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What does TLC stand for in chemistry, and what is it used for?

TLC stands for thin-layer chromatography. It is used to separate the substances in a mixture.

In TLC, what is the stationary phase and where is it found?

The stationary phase is a thin layer of solid, such as silica or alumina, spread on a flat plate.

In TLC, what is the mobile phase?

The mobile phase is the solvent, or mixture of solvents, that moves up the plate and carries the spots.

Why do you draw the start line in pencil on a TLC plate?

You use pencil because the graphite does not dissolve in the solvent, so the line stays in place.

Where should the solvent level be when you place a TLC plate in the beaker, and why?

The solvent level must be below the pencil line so the sample spots do not wash off into the solvent.

What is meant by the solvent front in TLC?

The solvent front is the highest point reached by the solvent on the TLC plate.

List the main steps in setting up a TLC experiment.

Draw a pencil line near the bottom. Place small spots of samples on the line. Stand the plate in a little solvent below the line. Cover the beaker and let the solvent rise. Remove the plate and mark the solvent front in pencil, then let it dry.

How can you tell from a TLC plate if a sample is pure or a mixture?

A pure substance gives one spot on the plate. A mixture gives two or more spots.

How can TLC be used to check if an unknown sample is the same as a known substance?

Spot both samples on the same plate and run the TLC. If their spots line up in the same positions, they are likely the same substance.

Give one advantage of TLC compared with paper chromatography.

TLC can separate mixtures more clearly and in less time than paper chromatography.