F214 Chromatography

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  • Created by: Amira200
  • Created on: 04-06-16 10:36
What is chromatography
An analytical technique used to separate components in a mixture
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What is chromatography used for
Analysis of drugs, plastics and flavourings
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What is meant by the mobile phase
The phase that moves in chromatography
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What is meant by the stationary phase
The phase that does not move in chromatography
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In TLC what state is the stationary phase
Solid
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In TLC what state is the mobile phase
Liquid
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In GC what state is the stationary phase
Liquid or solid on a solid support
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In GC what state is the mobile phase
Gas
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How does a solid stationary phase separate by
Adsorption
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How does a liquid stationary phase separate by
Relative solubility
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What is Thin Layer Chromatography
A method that monitors the extent of a chemical reaction/the purity of compounds
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What is the stationary phase in TLC
Silica gel or alumina (Al2O3)
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What is the mobile phase in TLC
A liquid solvent
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How do you work out the Rf value
Distance moved by component/distance moved by solvent front
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What are the limitations of TLC
Similar compounds have similar Rf values. Unknown compounds have no reference Rf for comparison. Difficult to find a solvent that separates all components in a mixture
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What is Gas Chromatography
A technique used to separate volatile components in a mixture
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What is GC particularly useful for
Organic compounds with a low BP and evaporate easily
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What is meant by the retention time
The time taken for the component to pass from the column inlet to the detector
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How can retention times be used
Retention times can be compared with those of known compounds to help in the identification an unknown substance
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What does the area under each peak in a GC tell us
It is proportional to the amount of a compound in the sample
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Limitations of GC are....
Similar chemicals may have same/similar retention times. Not all substances in sample will be separated and detected. unknown compounds have no reference retention time for comparison
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How can you improve reliability in a GC
Check results against a GC analysis of a reference sample containing only the suspected substance
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Why is gas chromatography combined with mass spectroscopy
Provides a far more analytical tool than GC alone. GC can separate components in a mixture but cannot identify them conclusively. MS can provide detailed structural info on most compounds for exact identification but cannot separate them
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What are the uses of GC-MS
Forensics, airport security, drug analysis, environmental analysis and space probes
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Other cards in this set

Card 2

Front

What is chromatography used for

Back

Analysis of drugs, plastics and flavourings

Card 3

Front

What is meant by the mobile phase

Back

Preview of the front of card 3

Card 4

Front

What is meant by the stationary phase

Back

Preview of the front of card 4

Card 5

Front

In TLC what state is the stationary phase

Back

Preview of the front of card 5
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