AQA GCSE FOUNDATION Chemistry: Chromatography Basics

Chromatography Basics

Chromatography is a powerful technique used to separate mixtures. It works by exploiting the different affinities of the components in a mixture for two phases: a stationary phase and a mobile phase.

How it works:

1. Stationary Phase: This is a solid or a liquid that is fixed in place, often a paper strip or a silica gel column. The stationary phase interacts with the components of the mixture.

2. Mobile Phase: This is a liquid or a gas that moves through the stationary phase, carrying the components of the mixture with it.

3. Separation: Different components of the mixture will have different affinities for the stationary phase. Components that are more attracted to the stationary phase will move more slowly, while components that are more attracted to the mobile phase will move more quickly. This results in the separation of the mixture into its individual components.

Types of Chromatography:

There are many different types of chromatography, but two common types are:

• Paper Chromatography: This type of chromatography uses a strip of paper as the stationary phase. The mobile phase is a solvent that travels up the paper by capillary action.

• Column Chromatography: This type of chromatography uses a column packed with a solid stationary phase. The mobile phase is a liquid that flows through the column.

Example: Paper Chromatography

Imagine you have a mixture of different coloured inks. To separate the inks using paper chromatography:

1. Prepare the paper: A piece of filter paper is dipped in a solvent (like water or alcohol) and suspended in a container, leaving a space at the bottom.

2. Apply the mixture: A small dot of the ink mixture is placed near the bottom of the paper.

3. Develop the chromatogram: The solvent travels up the paper, carrying the ink components with it.

4. Observation: As the solvent travels, the different ink components will separate into bands of different colours. This happens because the different ink components have different affinities for the paper (stationary phase) and the solvent (mobile phase).

Applications of Chromatography:

Chromatography has a wide range of applications in science and industry, including:

• Analyzing mixtures: Identifying and quantifying the components of a mixture
• Purification of substances: Isolating specific components from a mixture
• Drug testing: Identifying and quantifying drugs in biological samples
• Environmental monitoring: Detecting pollutants in air, water, and soil

Key Takeaways:

• Chromatography separates mixtures by exploiting the different affinities of the components for the stationary and mobile phases.
• Paper chromatography and column chromatography are two common types of chromatography.
• Chromatography has various applications in different scientific fields.