Chromotography Flashcards
What are the two types of chromotography?
-Thin layer chromatography (TLC)
-Gas chromatography
What are the two phases in chromatography? Explain both of them.
-Stationary Phase, Doesn’t move
-Mobile Phase, Does move
Explain TLC solid stationary phase?
-Separation is by adsorption, stronger the adsorption the less the components will move, more components slow down.
What is the stationary phase in TLC made out of?
-Silica or Alumina
How do you calculate Rf value?
Distance travelled by solute/ Distance travelled by solvent front
What are locating agents? and give examples of them.
-When you can’t see the spot.
-Iodine, however aromatic compounds need UV light.
What are the two types of gas chromatography?
-Gas solid
-Gas-liquid
What are the requirements for gas chromatography?
-Inert gas, inject sample into an oven.
What technique does Gas solid undergo? What is it made from?
-Adsorption, Silica
What technique does Gas-liquid undergo? What is it made from?
-Relative solubility, A high boiling point hydrocarbon
List the key points when you work out Gas chromatography.
-Injection of sample and vaporization
-Mobile carrier gas flushes it through the column
-Samples separated by relative solubility or adsorption
-Different compounds have different retention times
How do you interpret a gas chromatagram?
-Number of peaks = Number of compounds
-Approximate proportion of each compound is present by area
-Retention time = Indicated by position of peak interaction with stationary phase.
List some limitations of Chromatography
-Similar compounds often have similar retention times
-Unknown Compounds have no reference value
