Chromatography Flashcards
What is the mobile phase
The solvent eg water
What is the stationary phase
Whatever the solvent is travelling up eg filter paper
What are the two factors that effect distance travelled by solute
- Retention by stationary phase
- Solubility by moving phase
Describe a non polar molecules movement
- greater solubility in moving phase
- less retention by stationary phase
- so held in stationary phase for less time (will travel further)
Describe a polar molecules movement
- less solubility in moving phase
- greater retention by stationary phase
- so held in stationary phase for longer (will travel less)
In gas chromatography what states are the mobile and stationary phases
Mobile - gas
Stationary - liquid
If the stationary phase was polar and moving phase was non polar what type of compounds would travel further/quicker
Non polar compounds because they have greater solubility in the moving phase
Why do you use a pencil line
Will not dissolve in solvent
Why do you use a capillary tube to get a tiny drop of solution
Too big of a drop will cause different spots to emerge
Why only 1cm depth of solvent
- It must be below start line
If the solvent is too deep it will dissolve the mixture from the plate
What do you use if the spots are colourless and not visible
UV lamp
In gas chromatography why is it important to use an inert gas
So it doesn’t react with the compounds being separated in the column
Why does gas chromatography work
- different retention times
- different balance between solubility in moving phase and retention by stationary phase
Why is the plate left to dry in a fume cupboard
Solvent is toxic
How to locate position of amino acids
- spray with a developing agent
- work out Rf value
Why do you use a lid
To prevent evaporation of toxic solvent
Suggest a suitable reagent for the hydrolysis of a protein
Conc HCl
Why is it necessary to use two different solvents for amino acids
Some amino acids didn’t dissolve with the first
Is it essential to allow the solvent to reach all the way to the top to calculate a Rf value
Not essential but will make Rf value more accurate
Why do amino acids have different Rf values
- they have different polarities
- so different retention to stationary phase and solubility in mobile phase
What happens if your sample is too concentrated?
The spots will overlap
