Gas Chromatography Flashcards

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What is gas chromatography?

Gas chromatography is a method used to separate and analyse mixtures of gases or vapours.

What type of substances are usually separated by gas chromatography?

Gas chromatography is used for gases or liquids that easily turn into vapour, called volatile substances.

In gas chromatography, what is the mobile phase?

The mobile phase is an unreactive carrier gas that moves through the column and carries the sample with it.

In gas chromatography, what is the stationary phase?

The stationary phase is a high boiling point liquid coated on a solid inside a long column.

How does gas chromatography separate the substances in a mixture?

Different substances are carried through the column at different speeds, because they have different attractions to the stationary phase, so they come out at different times.

What is meant by the retention time in gas chromatography?

The retention time is the time taken for a substance to travel through the column and reach the detector.

How can you tell from a gas chromatogram if a sample is pure or a mixture?

A pure substance gives one peak on the chromatogram, while a mixture gives two or more peaks.

What does the number of peaks on a gas chromatogram tell you?

The number of peaks shows how many different substances are present in the mixture.

What does the size or area of a peak in a gas chromatogram show?

The size or area of a peak shows the amount of that substance in the mixture.

How can gas chromatography help identify an unknown substance?

You can compare its retention time to retention times from known substances under the same conditions.

Give one real-life use of gas chromatography.

Gas chromatography is used to test blood for drugs, or to check the purity of chemicals in industry.

What is GC-MS and why is it useful?

GC-MS is gas chromatography linked to mass spectrometry, and it can both separate substances and identify them very accurately.