Exam (elaborations)

BTEC Applied Science Unit 2C Undertake chromatographic techniques to identify components in mixtures

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Module
Unit 2

Institution
PEARSON (PEARSON)

This is the BTEC Applied Science Unit 2 Assignment : Undertake chromatographic techniques to identify components in mixtures, which was awarded a distinction . This is an example of a assignment which was awarded Distinction level, you may use it as a guide to help you achieve a distinction. Good L...

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Unit 2 Assignments A,B,C,D

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Unit 2 Learning Aim C Undertake chromatographic techniques to identify components in mixtures.

I have been newly appointed as a technical assistant at chemical equip, a large chemical plant. As part of my
induction period, I have been asked to demonstrate skills in a range of practical procedures and techniques.
This will also allow me to progress in my role. Regularly my company is required to identify substances. I have
been asked to write a report about the different techniques I have used when carrying out different
chromatographic techniques in order to separate and identify the components in mixtures. In my report I will
also need to analyse and evaluate my results and suggest improvements.

What is Chromatography?

Chromatography is a very important technique, this is because it allows molecules in mixtures to be separated
and identified, which helps carry out further analysis. There are various types of chromatography techniques
these include paper chromatography and TLC chromatography.

What factors affect separation?

There are also many factors which can have an effect on the separation of mixtures, during chromatography
these include the partition and absorption of molecules, or the differences between the weights of the
molecules. Another factor which affects separation is the size and polarity of the molecules as this can have an
effect on the distance the compound travels. As bigger molecules will take a longer period of time to move up
the chromatography paper, however smaller molecules will take a shorter period of time to move.

Difference between Thin layer chromatography and Paper chromatography?

When carrying out Paper Chromatography only a small amount of sample is required, however when carrying
out thin Layer chromatography, a larger sample is required. For Thin layer chromatography the separation
process takes a lot more time to complete, however for Paper chromatography the separation can be carried
out in less time. Another difference is that paper chromatography provides you with a vague separation,
however the separation of mixtures using TLC chromatography, provides you with clear, detailed, and distinct
results.

Why should paper chromatography be used and why?

Paper chromatography can be used, for different purposes in order to determine the purity of various products
and substances. It is commonly used to separate complex mixtures, into the various components. Paper
chromatography is also commonly used as it has many advantages such as, it only takes a small period of time
for the separation to occur, and this is a convenient factor for most individuals as it is less time consuming.

Why should Thin Layer Chromatography be used and why?

Thin layer chromatography is also commonly used in order to analyse the purity of various samples, by
separating the mixtures into various components. One advantage of thin layer chromatography is that multiple
samples can be analysed at the same time. However, there are also disadvantages of carrying out thin layer
chromatography, for example it takes a longer period of time for the separation to occur, and this can be an
inconvenient factor for most individuals as it is time consuming.

Different ways stains can be shown on chromatogram?

In order to view the spots on the chromatogram more clearly, various stains can be used as they can make the
results more visible to the human eye. This can be done by adding a stain such as a coloured dye to the
Chromatograms, an example of this is in order to find the various components of amino acids, the
chromatogram has to be sprayed with a solution called ninhydrin, the reason for this being that amino acids
are otherwise colourless therefore it would be hard to analyse results without using a dye. Once the ninhydrin
dye has been used on the chromatogram the compound will be stained purple.

UV light is needed to accurately view a chromatogram when a stain has been added. However, Fluorescence
can also be used, to view the chromatogram when a stain has been added, this is by shining the fluorescent

, light directly onto the chromatogram, as this will make the spots on the chromatogram glow this causes them
to be more visible to the eye.

What steps in your method and preparation were done to get the most accurate results, how would you stop
streaking and slanting?

When preparing my sample, I made that it was entirely dissolved in the solvent as this made sure I received
accurate and distinct separation. However, if my sample was not fully dissolved this could had meant that the
compounds did not interact with the stationary phase, which would have led to me receiving a slanted
chromatogram and inaccurate data.

when carrying out my experiment I took time, whilst adding my pigment to my chromatography paper by
allowing my pigment to dry before I added to it. This prohibited my spot from becoming excessively large,
which then prevented it from merging, and leaving me with inaccurate results. Another way which I prevented
streaking and slanting was by wearing gloves during the experiment, when handling my chromatogram in
order to protect my fingerprints from interfering with my chromatogram, as they acted like a barrier with the
chromatography paper.

Paper chromatography of photosynthetic pigments

Risk Assessment

Risk Hazard Precaution

Glass Apparatus Can be broken, and can cause Be precautious and wear
severe cuts and bleeding appropriate PPE
Petroleum Spirit Can be irritant and harmful to the Avoid contact with skin/ Wear
skin and are highly flammable. appropriate equipment.
Harmful to environment Do not empty down sink

Propanone Flammable, and if inhaled can Wear Eye protection and try not
cause dizziness and fatigue. to inhale.
Harmful to environment Do not empty down sink

Equipment

Grass

Propane

Sand

Pestle and mortar

Pencil

Ruler

Chromatography paper

Wooden stick

Solvent / Petroleum spirit and propane

Method

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