Unit 2- Practical Scientific Procedures and Techniques
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Assignment Unit 2 Learning Aim C - Chromatography
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Unit 2- Practical Scientific Procedures and Techniques
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PEARSON (PEARSON)
This is coursework for Unit 2 Practical Scientific procedures and techniques and is Learning aim C - Chromatography. This was graded a DISTINCTION with NO FEEDBACK. Work is to an optimum level. Good luck with writing!
Unit 2- Practical Scientific Procedures and Techniques
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Chromatographic Techniques to Identify Components in Mixtures
Chromatography is a method for separating a mixture of coloured solutes in a dye. It identifies
substances present in the mixture. The paper is immersed in a solvent containing many soluble
components. The solvent penetrates the paper and diffuses along it dissolving the various components
in the sample. The more soluble a component is, the higher up the paper it moves. If the sample
contains more than one colour, it must have more than one type of component.
paper chromatography | Definition, Method, & Uses | Britannica
In this report, I will be outlining the following chromatography techniques I used to separate and
identify components in a mixture: Paper chromatography of extracted plant pigments, thin layer
chromatography (TLC) of extracted plant pigments, and paper chromatography of amino acids. I will
thereafter analyse and evaluate my results and suggest any improvements that could be made to make
the experiment more accurate and precise.
Risk Assessment
Risk How to Prevent Likelihood Severity
Acetone (flammable) Keep away from flames 2 5
Acetone (irritable) Wear PPE 3 4
Gloves
Lab coat
Slips, trips, falls Chairs under desks 3 4
No running in the lab
Sharp implements - Be made aware of hazards 3 3
scissors First aid box available
Moving around and Area around to be clean and 5 4
manual handling organised
Use correct technique for lifting and
passing
Glassware, broken Hold safely 4 3
beakers, capillary tubes Keep away off the edge
Developing the chromatogram
The chromatogram is the paper or thin layer plate. The solvent font is marked with a pencil line.
Coloured spots are marked in case the colour fades. Invisible spots can be viewed using a UV lamp and
are marked, whereas some spots need to be developed using a chemical spray that causes a colour
change.
Paper chromatography
, Paper chromatography is used to separate mixtures of dissolved chemical substances. It is usually used
to test the purity of compounds and identify substances. It can also be used to separate complex
mixtures of amino acids, carbohydrates, steroids and peptides. In paper chromatography, the stationary
phase is a very uniform absorbent paper. The mobile phase is a liquid solvent or mixture of solvents that
moves through the paper.
https://www.bbc.co.uk/bitesize/guides/zqc6w6f/revision/4
In the first experiment, I separated the different pigments present in a leaf using paper chromatography.
Equipment:
• Pestle and mortar
• Chromatography paper
• Beaker (100cm3)
• Capillary tube
• Pencil
• Leaves
• Propane
Method:
1. Using a pestle and mortar crush up a few pieces of leaves. Add a pinch of sand inside to make
the process easier.
2. Once mostly crushed, add a few drops of propanone, and continue mixing, until the mixture
becomes slightly liquidly.
3. Draw a 3cm line up from the paper. Using a glass picker, put a few drops of the mixture on the
line.
4. Allow the spot to dry, then add another dot on top. Add five more drops of solution, letting
each one dry before putting on the next. This should build up a very concentrated small spot on
the paper.
5. Then fill a beaker with about half a cm of propanone and place the paper in the water.
6. Leave the experiment until the propanone has soaked near to the top, and then remove the
paper from the beaker.
7. Mark how high the propanone gets on the paper with a pencil and let the chromatogram dry.
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