CD.8 Flashcards
Using GLC to analyse mixtures
What are the two different phases in any type of chromatography?
Mobile phase and stationary phase.
What is the mobile phase of gas-liquid chromatography?
An inert or unreactive gas, known as the carrier gas.
What are examples of carrier gas used in GLC?
Helium, nitrogen, argon or hydrogen.
What is the stationary phase of GLC?
A high boiling point liquid held on a finely divided inert porous solid support.
Where are the phases held in GLC?
Inside a long thin tube known as a column which is coiled inside an oven.
What is an important feature of the oven in GLC?
Thermostatic. Meaning that the temperature is kept at a constant.
If a compound is more volatile, which phase will it favour?
Mobile phase.
If a sample is less volatile and more soluble, which phase will it favour?
Stationary phase.
How long would it take for a volatile compound to emerge?
Not very long, they will get carried along quicker in the mobile phase and emerge first.
How long would it take for a less volatile compound to emerge?
Much longer, they will spend more time dissolved in th stationary phase and will come out last.
What is Kpc?
The partition coefficient, it shows the distribution of components of a sample betweent the two phases.
What is the equation of Kpc?
Kpc = [component in stationary phase] / [component in mobile phase]
What does a high value of Kpc suggest about the component?
It favours the stationary phase more.
What does a low value of Kpc suggest about the component?
It favours the mobile phase more.
What is a chromatogram?
The plotted data of signals from the detector as compounds come out of the column.
