Chromatography Flashcards

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1
Q

What is chromatography used for?

A

It is used to separate individuals of a mixture and subsequently identify them

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2
Q

Describe how thin layer chromatography of photosynthetic pigments can be carried out

A
  • crush plant in pestle and mortar and add a solvent e.g. acetone
  • draw a pencil line near the bottom of the silica gel
  • using a capillary tube, drop sample onto centre of pencil line
  • repeat 10 times, allowing for drying inbetween
  • place in solvent ensuring line of solvent is below pencil line
  • seal chromatogram in jar with solvent
  • remove before solvent reaches top of chromatogram
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3
Q

What is used to identify substance from a chromatogram?

A

Rf values

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4
Q

How can Rf values be calculated

A

distance moved by pigment from origin/ distance moved by solvent front from origin

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5
Q

What does Rf stand for?

A

Relative front

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6
Q

What affects the rate at which substances move?

A
  • solubility in the solvent used
  • size of the molecule
  • polarity of the molecule
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7
Q

What is the stationary phase in TLC?

A

Silica gel

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8
Q

What is the mobile phased in TLC?

A

The solvent

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9
Q

How can an Rf value be used to identify a substance?

A

The Rf value of a certain molecule in a certain solvent can be looked up in a table of values and compared

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10
Q

How is 2 way chromatography completed?

A
  • normal one way chromatography is run

- the chromatogram is then turned 90 degrees and a different solvent is used

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11
Q

Why is 2 way chromatography used?

A

When substances in the chromatogram have similar Rf values and need further separation

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