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26 Cards in this Set
- Front
- Back
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What is chromatography?
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Chromatography is an analytical technique that separates components in a mixture between a mobile phase and a stationary phase.
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What state might the mobile phase be in?
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Liquid or gas
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What state is the stationary phase in in TLC?
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Solid
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What state is the stationary phase in in gas chromatography?
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Liquid or solid on a solid support
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How does a solid stationary phase separate components?
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By adsorption
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How does a liquid stationary phase separate components?
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By relative solubility
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Name some examples of a stationary phase in TLC
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Silica gel/alumina
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Name some examples of a TLC plate
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A sheet of glass or plastic
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Name a common solvent used in TLC
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Ethanol
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Define the Rf value
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Rf = distance moved by component/distance moved by solvent front
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Name 3 limitations of TLC
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1) Similar compounds have similar Rf values
2) Unknown compounds have no reference for Rf comparison 3) May be difficult to find a solvent that separates all the components in the mixture |
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What is gas chromatography?
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A technique used to separate volatile components in a mixture
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What is usually the mobile phase in gas chromatography?
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And inert or unreactive carrier gas
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Define retention time
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The time for a component to pass from the column inlet to the detector
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What does the area under a peak on a gas chromatograph tell you?
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The amount of a compound in the sampe
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Name 3 limitations of GC
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1) Many chemicals have the same retention time
2) Not all substances will necessarily be separated and detected 3) Unknown compounds have no reference retention times for comparison |
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What can GC do that MS can't?
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Separate components in a mixture
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What can MS do that GC can't?
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Provide detailed structural information for exact identification
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Why is combining GC and MS better than using them individually?
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It provides a more powerful analytical tool
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What can you do with a generate mass spectrum?
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Compare it with a spectral database by computer
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What are 4 uses for mass spectrometry?
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Forensics, environmental analysis, airport security and space probes
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Define phase
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A physically distinctive form of a substance, such as solid liquid and gaseous states of ordinary matter
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Define mobile phase
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The phase that moves in chromatography
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Define stationary phase
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The phase that does not move in chromatography
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Define adsorption
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The process by which a solid holds molecule of a gas or liquid or solute as a thin film on the surface of a solid
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What is a chromatograph?
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A visible record showing the result of separation of the components of a mixture by chromatography
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