Solvents in Chromatography Flashcards

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In chromatography, what is the solvent?

The solvent is the liquid that moves up the paper and carries the sample substances with it.

What is the solvent called in chromatography, mobile phase or stationary phase?

The solvent is called the mobile phase because it moves.

Why must the level of solvent be below the start line with the spots in paper chromatography?

So the sample spots do not dissolve straight into the solvent and wash off the paper at the start.

Why is it important to choose a suitable solvent in chromatography?

Because the solvent must dissolve the substances enough so they move, but not so much that they all move together.

What happens if the solvent does not dissolve the substances in the sample?

The spots will hardly move from the start line, so the substances will not separate.

What happens if all the substances are very soluble in the solvent?

The spots may all move with the solvent front and not separate well.

Give one common solvent used in paper chromatography and state when it might be used.

Water is a common solvent and is used for samples that dissolve well in water, such as many food colourings.

Why might ethanol or another organic solvent be used instead of water?

Ethanol or other organic solvents are used when the sample does not dissolve well in water.

Why are mixtures of solvents sometimes used in chromatography?

Mixtures of solvents can give better separation because they can dissolve different substances by different amounts.

How does the solvent help to separate substances on the paper?

The solvent carries each substance up the paper; substances that are more soluble in the solvent move further than those that are less soluble.