Analysis Flashcards
What does TLC stand for?
Thin-layer chromatography
What is the stationary phase in TLC?
Solid- Metal or glass
SP Silica
What is the mobile phase in TLC?
Solvent.
Why is chromatography used?
It is good at separating out components with similar properties.
Used to analyse drugs, flavourings and plastics.
What does GC stand for?
Gas chromatography
What is the stationary phase in GC?
A solid or a liquid.
What type of separation occurs in TLC?
Adsorption
What type of separation occurs in GC?
Relative solubility and adsorption.
What happens if the components are colourless?
Use UV light in the dark, to circle the spots with a pencil.
Spray ninhydrin onto the plate.
What are the limitations of TLC?
- Similar compounds have similar Rf values.
- Unknown compounds with no reference to compare with.
- May need lots of trial and error to find a suitable solvent.
What does the Rf value allow us to do?
Allows the ability to identify Unknown compounds by comparison with Rf values of reference compounds/known.
What is GC is used for?
Used to separate volatile components in a mixture.
What is in the carrier gas supply?
An inert gas e.g helium or nitrogen
What are the limitations of GC?
- many compounds have similar/same retention times.
- some substances may not separate out/not detected.
- Unknown compounds may not have a reference to compare the retention time.
What are the uses of GC-MS?
Airport security- to detect explosives.
Space probes- to collect and analyse material on other planets.
- environmental analysis- to monitor and analyse organic pollutants in the environment.
-Forensics- identify presence of particles such as in illegal drugs at a crime scene.
