Chromatography Flashcards

1
Q

Stationary phase

A

Solid substance
Mixture passes over in order to separated

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2
Q

Mobile phase

A

Liquid or gas

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3
Q

High affinity to stationary phase

A

Travel slowly

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4
Q

Low affinity to stationary phase

A

Travel quickly

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5
Q

Highly soluble in mobile phase

A

Travel quickly with solvent

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6
Q

Low solubility in mobile phase

A

Travel slowly with solvent

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7
Q

TLC diagram

A

https://www.chemguide.co.uk/analysis/chromatography/thinlayer.html

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8
Q

Stationary phase in TLC

A

TLC plate
Thin piece of aluminium/glass coated in silica gel

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9
Q

Mobile phase in TLC

A

Solvent/eluant

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10
Q

What condition allows spots to become visible in TLC?

A

UV light/iodine/fluorescent dye

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11
Q

RF equation

A

RF= distance moved by component/distance moved by solvent front

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12
Q

Advantage of TLC

A

Faster than paper chromatography
Works on very small samples

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13
Q

Disadvantage of TLC

A

Similar compounds may have similar Rf values
Cannot be used to separate large quantities

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14
Q

Column chromatography uses

A

Narrow glass tube with spout and tap- column

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15
Q

Stationary phase in column chromatography

A

Column packed with powder such as silica

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16
Q

Mobile phase in column chromatography

A

Solvent/eluant

17
Q

How is the compound separated in column chromatography

A

Mixture and solvent run through column
Different components of mixture travel through stationary phase and once reached the bottom, can be collected into separate beakers

18
Q

Advantage of column chromatography

A

Larger quantities can be separated

19
Q

If there is a more polar compound, what would a more polar solvent mean?

A

Higher solubility to mobile phase
Travels quickly

20
Q

If there is a more polar compound, what would a more polar stationary phase mean?

A

Higher affinity to stationary phase
Travels slower

21
Q

Gas-liquid chromatography used to

A

separate complex mixtures of volatile compounds

22
Q

Mobile phase in GC

A

Carrier gas e.g. nitrogen or helium

23
Q

Stationary phase in GC

A

Solid/viscous liquid e.g. alkane, which lines the capillary column

24
Q

Why can we only explain separation in terms of affinity to the stationary phase?

A

Mobile phase is not a solvent

25
How do we record distance travelled with gas chromatography
Retention time- time is takes from point of injection for component to detector
26
Limitation to GC
Lots of chemicals may have similar retention times and peak shapes so cant be positively identified
27
GC-MS
Enables separation of complex mixtures AND Identification of each component of that mixture
28
Uses of GC-MS
Forensics Airport secuirity
29
Why do we wear plastic gloves holding TLC plate?
Essential – to prevent contamination from the hands to the plate
30
Why do we add developing solvent to a depth of not more than 1cm3?
Essential – if the solvent is too deep it will dissolve the mixture from the plate
31
Why do we allow the solvent to rise up the plate to the top?
Not essential – the Rf value can be calculated if the solvent front does not reach the top of the plate
32
Why do we allow the plate to dry in a fume cupboard?
Essential – the solvent is toxic  
33
Outline the steps needed to locate the positions of the amino acids on the TLC plate and to determine their Rf values.
Spray with developing agent or use UV Measure distances from initial pencil line to the spots (x) Measure distance from initial pencil line to solvent front line (y) Rf value = x / y