paper chromatography -identify unknown amino acids
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what is the first thing you would do
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draw a pencil line near the bottom of a piece of chromatography paper and put a concentrated spot of the picture of amino acids on it (point of origin)
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what is it best to do with the piece of chromatography paper
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best to carefully roll the pice of paper into a cylinder with the spot on the outside so it'll stand up
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one you have added the point of origin and rolled the paper what would you do
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add a small amount of prepared solvent to a beaker and dip the bottom of the paper into it (not the point of origin)
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what is the solvent you oddly use for amino acids
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mixture of butan-1-ol , glacial ethanoic acid and water
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where should the dipping of the paper in the solvent be done
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in a fume cupboard cover with a lid to stop the solvent evaporating
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what will happen as the solvent spreads up the paper
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the different amino acids move with it but at different rates so they separate out
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what should you do once the solvents nearly reached the top of the paper
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take the paper out of the solvent and mark the solvent front(distance travelled by solvent ) with a pencil
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once you have marked the solent front what can you do
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leave the paper to dry out before you analyse it
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why won't you be able to see amino acids on the paper
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because they aren't coloured
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what do you need to do to the amino acids before you are able to analyse them
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you have to spray the paper with ninhydrin solution to turn the amino acids purple
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where should the spraying of ninhydrin be done
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in a fume cupboard a gloves should be worn
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what does ninhydrin detect only
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proteins and amino acids
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what is the Rf value (value of amino acid )
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ratio of distance travelled by a spot to distance travelled by the solvent
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how do you work out Rf value
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distance travelled by spot /distance travelled by solvent
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when measuring distance travelled by spot what should you do
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measure from point of origin to vertical centre of spot
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how can you work out what was in the mixture
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by calculating the Rf value for each spot and looking each Rf value up in a database , or table of known values
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as well as looking up the Rf value in a database how else could you work out what was in a mixture
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-you could compare your chromatogram to the chromatogram of a known mixture and identify the components that way -if two spots have travelled the same distance in the solvent , they will be the same molecule
