5 Sept 2026 · Revise Right Team

Chromatography Types: TLC, CC & GC (Part 2/4) Revision Notes | A Level AQA Chemistry

Chromatography Types: TLC, CC & GC (Part 2/4): Explore the three main types of chromatography: thin-layer chromatography (TLC), column chromatography (CC),…

Chromatography Types: TLC, CC & GC (Part 2/4) is part of Chromatography (A-level only) in A Level AQA Chemistry.

1 min

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A Level AQA

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What this lesson covers

Chromatography Types: TLC, CC & GC (Part 2/4): Explore the three main types of chromatography: thin-layer chromatography (TLC), column chromatography (CC),…

Explain adsorption and partition in chromatography
Interpret how polarity affects movement in TLC and retention in GC
Compare applications and limitations of TLC, CC, and GC
Explain how GC can identify and quantify components in a mixture

Key ideas to keep in view

Use this lesson to stay inside Chromatography (A-level only) while connecting the detail back to the wider Organic chemistry topic.

Stationary phase: The phase that remains fixed during chromatography. In TLC and CC it is a solid adsorbent (typically silica); in GC it is a high-boiling liquid coated onto an inert solid support inside a column.
Mobile phase: The phase that moves through or over the stationary phase, carrying components of the mixture with it. In TLC and CC it is a liquid solvent; in GC it is an inert carrier gas such as nitrogen or helium.
Rf value: The retention factor — the ratio of the distance travelled by a component to the distance travelled by the solvent front in TLC. A dimensionless number between 0 and 1 used to identify compounds under fixed conditions.
Retention time: The time taken for a specific component to travel through the GC column and reach the detector, measured from injection. Used to identify components by comparison with known standards under identical conditions.

Revision notes

Read the core explanations from Chromatography Types: TLC, CC & GC (Part 2/4) before testing yourself from memory.

1. Adsorption, Partition, and Why Separation Happens

Chromatographic separation is often explained using two linked ideas: adsorption and partition. In TLC and column chromatography, substances may adsorb to the solid stationary phase to different extents. In GC, substances partition between the carrier gas and the stationary phase inside the column.

Worked example: Explaining Different Chromatography Outcomes

Why might one compound move quickly in TLC but have a long retention time in GC?

Movement depends on attraction to the stationary phase versus solubility in the solvent. — A compound can move quickly if it interacts weakly with the stationary phase under that solvent system.
Retention time depends on how strongly the compound partitions into the stationary phase inside the column. — The same compound may behave differently because the method conditions and phases are different.
Do not transfer conclusions directly from one chromatography method to another. — The interpretation must match the actual technique being used.

Answer: Chromatographic behaviour depends on the phases and conditions of the specific method, so a substance can behave differently in TLC and GC.

Technique	Main separation language	Useful output
TLC	adsorption / relative movement on a plate	Rf value and spot pattern
Column chromatography	different movement through packed stationary phase	separate fractions
GC	partition / retention in the column	retention time and peak area

At A level, the key is not to memorise the words adsorption and partition in isolation. It is to use them to explain why the observed Rf value, retention time, or peak area makes sense for the method being used.

Sources and content standards

Published by Revise Right. Use the official specification reference to check the requirements for your course. Content updated: 2026-09-05.

AQA A-level Chemistry (7405) specification How we check content Report a correction — include this lesson URL

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.

Interpreting NMR Spectra and Integration Spin-Spin Splitting and Analytical Techniques Chromatography Types: TLC, CC & GC (Part 3/4)Calculations in Chromatography: Rf and Retention Times (Part 1/4)Organic chemistry topic A Level AQA pathway

Frequently asked questions

What should I know about Chromatography Types: TLC, CC & GC (Part 2/4)?

What should I learn from this Chemistry lesson?

By the end of this lesson, you should be able to Explain adsorption and partition in chromatography; Interpret how polarity affects movement in TLC and retention in GC; Compare applications and limitations of TLC, CC, and GC; Explain how GC can identify and quantify components in a mixture.

How should I revise Chromatography Types: TLC, CC & GC (Part 2/4)?

Read each section, then close the notes and explain the idea from memory. Check your explanation against the page and finish with an exam question from Organic chemistry.

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