Analysis - Chromatography Flashcards
What is the mobile phase?
Where the molecules can move. It is always a liquid or a gas
What is chromatography?
An analytical method that is used to separate the substances in a mixture and then identify them
What is the stationary phase?
Where the molecules can’t move. This can be a solid or a really thick liquid
When does the substance being tested stop moving across the stationary phase?
Once the amount leaving the stationary phase for the mobile phase and vise versa are the same. They have reached a dynamic equilibrium
What two things does the amount of time the molecules spend in each phase depend on?
- How soluble they are in the solvent
2. How attracted they are to the paper
What assets will molecules have if they are carried further up the paper?
They will have a higher solubility and will be less attracted to the paper
What is the stationary phase in thin layer chromatography?
A thin layer of solid (e.g silica gel)
What is the result of chromatography analysis called?
A chromatogram
What are the spots of substance on the chromatogram called?
Solutes
What is the formula to work out the Rf value
Rf = Distance travelled by solute
——– (Divided by) ———
Distance travelled by solvent
What do chemists often use to compare the substance under test to?
Standard reference materials (SRMs) which have carefully controlled concentrations and purities
What is the mobile phase is gas chromatography?
An unreactive gas such as nitrogen
What is the stationary phase is gas chromatography?
A thick liquid such as an oil
What is the first stage of gas chromatography?
The unknown mixture is injected into a long tube coated on the inside with the stationary phase
What is the second stage of gas chromatography?
The mixture moves along the tube with the mobile phase until it comes out the other end. The time it takes a chemical to travel through the tube is called the retention time.
