What is chromatography used for?

Chromatography is a method used to separate individual components from a mixture of substances.

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What is meant by the term stationary phase

The stationary phase is the phase that does not move in chromatography.


The stationary phase is typically a solid, or a liquid supported on a solid.

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What is meant by the term mobile phase?

The mobile phase is the phase that moves in chromatography, carrying the mixture through the system.


The mobile phase is typically a liquid or a gas.

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What are the stationary and mobile phases in thin-layer chromatography?

The stationary phase is the adsorbent which is typically a thin layer of silica or alumina on a solid support of glass or metal.

The mobile phase is a solvent or solvent mixture.

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How does thin-layer chromatography separate the components of a mixture?

Thin-layer chromatography separates the components of a mixture based on their differing strengths of adsorption to the stationary phase and their differing adsorption strengths to the stationary phase and solubilities in the mobile phase, causing them to travel up the plate at different rates.

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What two factors affect separation in thin-layer chromatagraphy?

  1. The affinity of each component for the stationary phase.
  2. The solubility of each component in the solvent (i.e. mobile phase).

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What is meant by the retention factor (Rf) value?

The retention factor (Rf) value is is the ratio of the distance travelled by a component (spot) from the baseline to the distance travelled by the solvent front.


These distances are represented on the chromatogram below.

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What is the formula to calculate Rf values?

Rf ​=distance travelled by solvent distance travelled by spot​

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What is the range of Rf values in thin-layer chromatography?

Rf values range from 0 to 1.

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What are the stationary and mobile phases in gas chromatography?

The stationary phase is a non-polar high boiling liquid absorbed onto a solid support. 

The mobile phase is an inert carrier gas such as helium or neon.


Gas-liquid chromatography is also referred to as gas-chromatography.

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How does gas chromatography separate the components of a mixture?

In gas chromatography, the components of a vaporised sample are carried by an inert gas through a column coated with a liquid stationary phase. Components separate based on how they partition between the mobile gas and the stationary phase.

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What is meant by the term rention time?

Retention time is the time taken for each component to travel through the gas chromatography column before reaching the detector.

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What two pieces of information can be obtained from a gas chromatogram?

  1. Components in a mixture can be identified using retention times.
  2. The percentage composition of a mixture can be determined using peak areas.

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How can Rf values and retention times be used to identify different substances in a mixture?

The Rf values and retention times can be compared to known values for pure substances to identify components in a mixture.

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How can you calculate the percentage composition of a mixture using gas chromatography?

Calculate the area under each component's peak as a percentage of the total area under all peaks.

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