CCEA A-Level Chemistry 1110
Formulae, Equations and Amounts of Substance
Atomic Structure
Bonding
Intermolecular Forces and Structure
Shapes of Molecules and Ions
Redox
The Halogens
Acid-Base Titrations
Qualitative Tests
Formulae and Amounts of a Substance
Nomenclature and Isomerism in Organic Chemistry
Alkanes
Alkenes
Halogenoalkanes
Alcohols
Infrared Spectroscopy
Energetics
Kinetics
Equilibrium
Group II Elements and Their Compounds
Lattice Enthalpy, Entropy and Free Energy
Rates of Reaction
Equilibrium and Acid-Base Equilibria
Isomerism
Aldehydes and Ketones
Carboxylic Acids
Derivatives of Carboxylic Acids
Aromatic Chemistry
Spectroscopy and Chromatography
Volumetric Analysis
Transition Metals
Electrode Potentials
Amines
Amides and Polymers
Amino Acids and Proteins
Spectroscopy and Chromatography
Gas–liquid chromatography
- 3 things to know
- Unit A2 2
Overview
Two phases in gas–liquid chromatography, two gases used as the carrier and retention time.
What you need to know
Answer each one before you reveal it.
Name two gases used as the carrier in gas–liquid chromatography
Why is the column in gas–liquid chromatography held in an oven?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What are the two phases in gas–liquid chromatography?
Model answer
A high boiling liquid held on an inert solid support inside the column is the stationary phase, and an unreactive carrier gas is the mobile phase.
- 2
Name two gases used as the carrier.
Model answer
Nitrogen and helium.
- 3
Why must the carrier gas be unreactive?
Model answer
It must move the sample through the column without reacting with it or with the stationary phase.
- 4
Why is the column held in an oven?
Model answer
The components must stay in the vapour phase to travel with the carrier gas, and a controlled temperature makes the retention times reproducible.
- 5
What determines how long a component takes to pass through?
Model answer
How volatile it is and how strongly it dissolves in the liquid stationary phase; a component that dissolves readily is held back.
- 6
What is the retention time?
Model answer
The time between injection and the appearance of that component at the detector.
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