Chromatography And Spectroscopy Flashcards
What is chromatography used for
Seperate mixtures of liquids with different solubilities
What are the two different components used in every chromatography
Stationary and mobile phase
Define stationary phase
Solid or liquid on solid that doesn’t move
Define mobile phase
Gas or liquid that does move
What are the types of chromatography
Thin layer and gas
What is the stationary phase in TLC
Adsorbent substance on plastic or glass
How does TLC work
Different components have different affinities for the adsorbent so adsorb to surface differently
Describe the method for TLC
Draw pencil base line 1cm from. Base of TLC plate.
Spot solution onto baseline using capillary tube
Add solvent to beaker 0.5 cm from base of plate
Add watch glass ontop
Leave until solvent front is 1cm from top
Remove plate and mark solvent front
Use UV lamp or iodine crystals to mark circles
Calculate r.f values and compare to database
What does r.f stand for
Retention factor
How do you calculate r.f values
Distance traveled by component / distance travelled by solvent front
What is gas chromatography used for
To seperate volatile components
How does GC work
Different components have different affinities for stationary phase
Slow down with higher affinity and adsorption
What component is eluted first in GC
Most volatile with less affinity for SP
What factors affect retention time GC
Type of carrier gas and flow
Length of column
Temp of column
Packing material (column material)
What affects r.f in TLC
Solvent and adsorbent
How can you calculate the concentration of a component from a GC scan
Plot calibration curve
X= conc Y= peak area
Use a dilution series
Compare area with conc
What does NMR. Stand for
Nuclear magnetic resonance
How does NMR use
Strong magnetic fields are used to allow radio waves to be absorbed my nuclei causing energy release from nucleus
On what types of atoms can NMR be used on
Those with odd núcleons
What is resonance
When the nucleus alternates between two spin states
One is aligned with and one against the magnetic field
Against= higher energy
Dropping back to lower energy causes energy release
What is the main advantage of NMR over chromatography
The compound can be recovered because it is not broken down.
How do you carry out NMR
Add sample to solvent
Spin to even put imperfections in megnetic field
Run NMR
Evaporate off solvent to obtain sample again
What solvent is used to prevent artefact peaks
Used deuterated Solvents
D is 2H so has no magnetic spin so will no show up in 1HNMR
E.g D2O not H2O
What must you quote in 13C NMR
What C environments are present
Chemical shift
How many different C environments are present
