Chemistry: 3.16 Chromatography
This flashcard set explains the fundamental principles of chromatography, highlighting the interaction between the stationary and mobile phases. It defines what a phase is, describes the movement of the mobile phase, and emphasizes the immobility of the stationary phase.
all forms of chromatography involve the distribution of the components of a mixture between which 2 phases
a stationary phase and a moving phase
Key Terms
all forms of chromatography involve the distribution of the components of a mixture between which 2 phases
a stationary phase and a moving phase
phase
a state such as solid, liquid or gas
what does the mobile phase pass over
the stationary phase
what doesn’t the stationary phase do
move
adsoprtion
the process by which a sold holds molecules onto its surface
what does TLC stand for
thin layer chromatography
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| Term | Definition |
|---|---|
all forms of chromatography involve the distribution of the components of a mixture between which 2 phases | a stationary phase and a moving phase |
phase | a state such as solid, liquid or gas |
what does the mobile phase pass over | the stationary phase |
what doesn’t the stationary phase do | move |
adsoprtion | the process by which a sold holds molecules onto its surface |
what does TLC stand for | thin layer chromatography |
what does cc stand for | column chromatography |
what does GC stand for | gas chromatography |
TLC: stationary phase | piece of card/filter paper TLC plate- silica/alumina coating |
TLC: mobile phase | various solvents used |
CC: stationary phase | glass column packed with a solid |
CC: mobile phase | a liquid solvent (eluent) moves down the column |
GC: stationary phase | solid/solid coated with lqiuid packed into a capillary tube |
TLC: mobile phase | unreactive carrier gas (eg He/N2) used under pressure at high temp |
separation of components: how does separation occur if the stationary phase is a solid | adsorption |
separation of components: what is the correlation between strength of adsorption and speed of component moving through mobile phase | the stronger the adsorption to the stationary solid phase, the slower the component moves through the mobile phase |
separation of components: how does separation occur if the stationary phase is a liquid |
|
separation of components: what is the correlation between solubility of liquid stationary phase and speed of component moving through mobile phase | the greater the solubility in the stationary liquid phase, the slower the component moves through the mobile phase |
separation of components: what is the rate of movement of a component recorded as and what can this be used to idetify | recorded as Rf value/retention time can be used to identify a component |
separation of components: what properties is the strength of adsorption and relative solubility of a molecule affected by | -charge |
separation of components: what does separation depend of the balance between | solubility in the moving phase and retention in the stationary phase |
TLC: uses | separation- identifying components in mixtures |
TLC: moving phase | solvent |
TLC: stationary phase | TLC plate |
TLC experimental details: dissolve a small sample of mixture in | solvent |
TLC experimental details: draw a … a short distance from the bottom of the TLC plate | pencil line |
TLC experimental details: place a spot of… on the pencil line and allow to dry | component |
TLC experimental details: place the TLC plate in a beaker containing a small amount of | the solvent |
TLC experimental details: cover beaker with | a lid |
TLC experimental details: allow solvent to rise up tlc plate and stop before | it reaches the top |
TLC experimental details: mark on the … in … once the solvent has risen almost to the top of the TLC plate | solvent front in pencil |
TLC experimental details: what can be used to make the compounds visible | locating agent |
TLC: locating agents | uv light, ninhydrin, I2 crystals, MnO4 |
TLC: advantages compared to paper chromatography |
|
TLC: limitations |
|
Rf | distance moved by spot/distance moved by solvent |
Rf values can only be between | 0 and 1 |
CC: uses | separating large amounts of mixtures |
CC: moving phase | liquid solvent which passes down and out of column (eluent) |
CC: stationary phase | solid beads |
CC experimental details: fill a glass tube with | stationary phase, held in place by a filter or mineral wool plug |
CC experimental details: cover all powder in | solvent |
CC experimental details: dissolve mixture to be sampled in | minimum amount of solvent |
CC experimental details: place mixture on top of | solid phase |
CC experimental details: run mixture through column by | opening tap and adding solvent at the top |
CC experimental details: time taken for each component to reach end of column recorded, this is known as | retention time |
CC: advantages | -used for larger amounts of sample |
GC: what kind of method is GC | a very sensitive quantitative method |
GC: uses | to test a wide range of compounds |
GC: moving phase | inert carrier gas at high temp and pressure |
GC: stationary phase | thin layer of solid/liquid- both in capillary tube |
GC experimental details: mixture injected into gas chromatograph where it | vapourises |
GC experimental details: what flushes mixture through the column | the carrier gas (moving phase) |
GC experimental details: why do the components slow down | as they interact with the stationary phase |
GC experimental details: each component leaves the column at a different time and is | detected |
retention time | the time taken for a component to pass from the column inlet to the detector |
correlation between retention time and components solubility in stationary phase | the longer the retention time, the greater the components solubility in the stationary phase |
why can retention times be theoretically used for identification | different compounds have different retention time values |
gas chromatogram: number of peaks= | number of components in the mixture |
gas chromatogram: area under each peak proportional to | amount of a component in the mixture |
limitations of GC: |
|
what does GCMS stand for | gas chromatography mass spectrometry |
what does combining gas chromatography with mass spectrometry give | a far more powerful tool than gas chromatography alone |
what is gas chromatography not good at despite being used to separate components | identifying structure |
GCMS: what is mass spectrometry used to do | identify the separated components |
GCMS: first stage | GC first used to separate components in the mixture |
GCMS: second stage | each separated compoentns directed to MS in turn |
GCMS: third stage | each mass spectrum can be analysed/compared with spectral database, so enabling compound to be identified |
GCMS: fourth stage | quantity of each component can also be determined |
what is a mass specturm | a plot of relative abundance against mass to charge ratio |
what does a mass spectrum consist of | a series of peaks at different masses corresponding to the mass of the whole molecule and the masses of the fragment ions |
what will the peak with the highest m/z ratio in a mass spectrum be down to | the molecular ion |
what does fragmentation provide in mass spectrums | structural detail |
uses of GCMS |
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