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Unit 2 Aim C
- Module
- Unit 2
- Institution
- PEARSON (PEARSON)
Applied Science BTEC Unit 2 Aim C Chromatography
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ChromatographyIntroduction:
Chromatography is used to separate mixtures, isolate one substance from the other substances
to analyse it further or to prepare it to use it in a separate way, there are two phases in
chromatography, the stationary phase which is the solid material that absorbs the mixture flowing
through it and the mobile phase which is the liquid that transports the substance mixture through
the absorbing material which travels along the stationary phase and carries the components with
it. This process occurs on a chromatogram which is the paper or plate which shows the substance
separation, a chromatogram is the stationary phase. The mobile phase depends on the solvent
that is used, and which chromatographic technique is being experimented with.
There are two types of chromatography that I investigated, Paper Chromatography and Thin Layer
Chromatography. In Thin Layer chromatography, compared to paper chromatography, the mobile
phase moves more quicker and evenly through the stationary phase. They also have more useful
chromatograms as they show greater separation of the components in the mixture than paper
chromatograms, so it makes them easier to analyse. In paper chromatography, the stationary
phase is paper, and the mobile phase is a liquid aqueous/ non aqueous solvent. In thin layer
chromatography, the stationary phase would be the plate and the mobile phase would be usually
an organic solvent.
There is also liquid chromatography and gas chromatography. Liquid chromatography is mostly
used by the pharmaceutical industry to provide precise results for drug products. Gas
chromatography is usually used to separate and measure organic molecules and gases, it is more
sensitive, so it allows for a more accurate determination of what chemicals are in a mixture and
the quantity.
, Plant Chromatography
Apparatus:
• 4 Spinach Leaves
• Acetone
• Acetone Petroleum
• Pipette
• Boiling Tube
• Pestle and Mortar
• Chromatography Paper
Method:
1. First, I tore up 4 large spinach leaves and put into a pestle and mortar along with a pinch
of sand and 5cm 3 of acetone and grinded all of this until I got a dark green chlorophyll
extract
2. Then, I measure the amount of chromatography paper I needed so that it fits into the
boiling tube without touching the sides or right to the bottom
3. I then marked a pencil line 1.5cm from the bottom of the paper and in the middle of the
line I marked a cross
4. From the top of the chromatography paper, I marked another line 2cm from the top of the
paper
5. Then, using the capillary tube I picked up some of the chlorophyll solution and placed it on
the cross, then after it dries repeat the process to make a small, dense spot
6. Using a pipette to avoid wetting the sides and reducing any accuracy of the investigation,
I put 1.5cm3 of acetone petroleum ether mix solvent into the boiling tube
7. Then, I suspended the chromatography paper using a drawing pin making sure then pencil
line is not in the solvent, just touches it
8. When the solvent reached the line at the top of the paper, I removed the chromatography
paper and marked the positions of the pigments before they faded away
9. Finally, using the markings I calculated the Rf values of the pigments and using the
reference table I identified the pigments
Set-up:
I set up the experiment in a way to make sure that I never got confused at any point, firstly, I got
everything I needed to make the dark green chlorophyll extract then once that was done and tidied
away, I then moved onto marking the chromatography paper and adding the chlorophyll solution.
Then, whilst waiting for the mixtures to separate, I tidied everything away and once the mixtures
reached the line at the top, I calculated the Rf values and identified them.
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