16O- Chromatography Flashcards
What’s chromatography used for
Separate and identify components in a mixture
What’s thin layer chromatography TLC
A plastic plate coated with a solid, a solvent moves up the plate
What’s column chromatography CC
Column packed with a solid, solvent moves down column
What’s gas chromatography GC
Column packed with a solid or a solid coated with liquid, gas is passed through column under pressure at a high temp
What’s the mobile phase
Solvent, carries soluble components
The more soluble a component the faster it is carried
What’s the stationary phase
The paper or substance on the paper
Holds back components in the mixture
The higher the affinity of a compound to the stationary phase the slower it will move
How are components in a mixture separated
Depends on the solubility of the components in the moving phase (solvent) and retention of the components to the stationary phase (paper/powder on paper)
What’s retention time
Time taken for a compound to go from it’s initial position when injected to the detector
Can be used to identify substances
Equation for Rf value
Distance moved by substance/ distance to solvent front
Repeat for each spot produced
This Rf value can identify the constituent substances within a compound when compared to standards
Method for TLC
1.Wearing gloves (stops contamination of plate) draw a pencil line (won’t dissolve in solvent) 2cm from the bottom of a TLC plate, mark equal spots for each of the substances across
2.Use a capillary tube to place a drop (don’t want substances to overlap) of solvent on each marking, let this dry
3. Add solvent to a beaker no more than 2cm in depth (need solvent to carry substances not dissolve them from the spot)
4. Place the TLc plate into the solvent ensuring the solvent doesn’t go over the line, place a lid over the beaker (solvent is toxic preventing evaporation)
5. Once the solvent is 1cm away from the top of the paper remove he chromatogram and mark the solvent front with pencil, allow it to dry in the fume cupboard (solvent is toxic)
6.place under UV light (spots are colourless) and mark the centre of the spots, calculate Rf value
What’s GC and mass spectroscopy used for
Mass spectroscopy is used as a detector for GC
A components comes out of a GC system after its retention time, this is noted, the compound is put into a mass spectrometer and identified by mass of fragmentation pattern
How does polarity effect chromatography
Is a solvent is polar and a compound is polar, the compound is more soluble increasing the mobile phase
If the stationary phase is non polar and the compound is non polar, they would move through slower as the compound has a higher affinity to the stationary phase
