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BTEC Applied Science Unit 2 Assignment C - Chromatography
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- PEARSON (PEARSON)
BTEC Applied Science Unit 2 Assignment C - Chromatography. Pictures, graphs, tables included. Distinction work
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Criteria covered by this task:Unit/Criteria
To achieve the criteria, you must show that you are able to:
reference
C.D3 Evaluate the chromatographic techniques used in relation to outcomes and
suggest improvements.
Analyse own chromatograms and relate the factors that affect the separation of
C.M3
mixtures to the quality of results obtained.
C.P5 Correctly use chromatographic techniques to produce chromatograms.
C.P6 Explain the use of chromatographic techniques to separate mixtures.
I Certify this is my own work
U2.C: Separate to identify
Thin Layer Chromatography of Spinach
Introduction:
Most leaves are green due to chlorophyll. This substance is important in photosynthesis (the
process by which plants make their food). In this experiment, the different pigments present in a
leaf are separated using paper and thin layer chromatography.
Method:
Preparing your pigment - https://www.youtube.com/watch?v=W56RHxu2Hpc
1. Set up 3 test tubes in a test tube rack, adding one spatula tip of sodium sulfate to tubes
1 and 3.
2. Tear up one spinach leaf and put the pieces into test tube 1.
3. Add 2 ml propanone to test tube 1. (Test tube 1 should now contain sodium sulfate,
spinach and propanone.)
4. Use the end of your spatula to ‘chop’ the mixture for a few minutes until you have a
deep green liquid amongst the leaf pieces.
5. Use a pipette to transfer the liquid ONLY into test tube 2.
6. Add 2 ml petroleum spirit to test tube 2. Upon agitation, the pigments will aggregate
into the petroleum layer on top.
7. Use a pipette to transfer the top layer into test tube 3. You will use this final
solvent/pigment mixture to create your chromatogram.
Creating your chromatogram
1. You should have a strip of Polygram chromatography sheet. Only hold it around the
edges. Draw a pencil line 1 cm up from the bottom edge.
2. Take a capillary tube and dip the end into test tube 3 to suck up some pigment mixture.
3. Apply one dot of this green mixture to the middle (or there-abouts) of the pencil line.
Wait 30 seconds for the alcohol to evaporate and apply another dot on top. Repeat this
step until you are left with a deeply pigmented dot around 4 mm wide.
4. Using a pipette, add 1 ml of eluting solvent (cyclohexane, hexane and propanone) to a
glass vial. Place your strip into the vial (the solvent should be lower than the pencil line
and dot of pigment. Replace the screw cap tightly and watch as the plate absorbs the
solvent and separates the pigments.
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