Unit 2- Practical Scientific Procedures and Techniques
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BTEC Level 3 Applied Science Unit 2- Practical Scientific Procedures and Techniques Learning Aim C | Chromatography - Distinction*
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Unit 2- Practical Scientific Procedures and Techniques
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PEARSON (PEARSON)
BTEC Level 3 Applied Science Unit 2- Practical Scientific Procedures and Techniques Learning Aim C | Chromatography - Distinction*
Learning Aim C assignment containing pass, merit and distinction.
Evidence included as well.
Unit 2- Practical Scientific Procedures and Techniques
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Voorbeeld van de inhoud
Unit 2 : Practical Scientific Procedures and Techniques
Assignment A : Keeping up with Standards
Introduction :
Chromatography is the technique of separating solutes that have different solubilities in a
given solvent. It consists of two phases, the stationary phase which means it does not move
and the mobile phase which means it can move. The paper is usually the stationary phase
and the solvent is the mobile phase. The molecules move up the paper through capillary
action. Solute is the ink, or the dye, solvent is the liquid, solubility means how easy it is for a
substance to dissolve and chromatogram is the paper once the experiment is finished.
The application of chromatography in real life may be, pharmaceutical testing, biochemical
analysis, drug testing, food testing and beverage testing. Chromatography can be used in
identifying the amino acids and separating proteins.
The equipment used in this diagram is beaker, a solvent, ink/dye and pencil. The diagram is
used for the solvent, essentially water to be added, the water should be more than above the
pencil line. On the chromatography paper you need to draw a pencil line which will be filled
with the ink or dye you want to experiment with. The solvent will travel up the paper and
spread the components of the ink or dye. Once it stops you will draw with a pencil the
solvent font, this is where the solvent stopped moving up the paper.
Thin Layer Chromatography
This type of chromatography consists of a TLC plate (thin layer chromatography) which
contains a thin layer of plastic and a thin layer of silica gel. This technique separates a
soluble substance from a liquid mixture. In this case, silica acts as the stationary phase, and
the solvent is the mobile phase as it is made to flow through the silica bed. Analytical
chromatography can be used to purify compounds nagging from milligram to gram scale.
TLC also uses a chamber whenever it is used in experiments as the solvent can dissolve
quickly.
This is the type of chromatography that we have used for this assignment. What we needed
to do is get silica gel paper and make sure that our sample was grinded correctly in order for
the pigment to be transferred to the paper. Then we placed the paper in the beaker which we
filled with our given solvent.
The solvent will separate the components and show us the different colours on the
chromatogram, the colours will need to be identified to what pigment group they belong to
and measure the distance of them.
Some of the components may not travel as far as they may be more attracted to the
stationary phase, therefore they are less likely to travel further as other substances which
are more attracted to the mobile phase.
The attraction between different phases can be due to polarity, absorption, adsorption and
solubility.
, Unit 2 : Practical Scientific Procedures and Techniques
Assignment A : Keeping up with Standards
Gas chromatography :
This type of chromatography consists of a carrier gas, flow controller, column oven, detector
and a recorder. This technique is used to separate complex mixtures based on their boiling
point, vapour pressure and polarity. A liquid sample will be injected into the oven, the oven
will then boil to make the sample to produce a vapour. This will lead to the vapour being
carried through a column which is a steel tube packed with porous rock. The molecules of
the sample will move with the gas, this would be known as the mobile phase, and through
the system which will lead to contact with a liquid solvent, which would be known as the
stationary phase, and this will be absorbed onto the solid material.
The time taken for the sample to pass through the machine to the detector on the column is
the retention time and this will depend on the sample's solubility. There are different types of
detectors, but the thermal conductivity detector uses the temperature difference of burning
between two streams of gas. The temperature of the oven is controlled at stages and helps
to provide an electrical resistance difference in order to find out what substance is used.
Ion-exchange chromatography :
This type of chromatography is used for amino acids, this consists of cation exchange and
anion exchange. This technique is used to process the purification of proteins and other
charged molecules in amino acids, this procedure may be used in water analysis.
The method relies on the attraction of oppositely charged ions between the mobile and
stationary phase. A low concentration salt mobile phase will interact with the stationary
phase ions weakly, therefore eluting first. Eluting means the extraction of one substance
from another using a solvent.
Cation exchange is the stationary phase being charged positively, the ionic interaction
between negatively charged ions in the sample and positively charged ions in the stationary
phase is strong, so they bind and become eluted.
Anion exchange is the stationary phase being charged negatively, proteins that are charged
positively will bind to the negatively charged and become eluted.
The pH of the mobile phase is important, if the pH is raised the number of available
hydrogen ions decreases and so the mobile phase becomes less positive. By lowering the
pH of the mobile phase the proton availability increases, thus making the mobile phase more
negatively charged.
Liquid chromatography :
This type of chromatography is used to separate proteins, nucleic acids or small molecules
in complex mixtures. This type of chromatography separates molecules in a liquid mobile
phase using a solid stationary phase. It can be used for analytical or preparative
applications. This technique is used to separate, identify and quantify unknown and known
compounds and elucidate the structure and chemical properties of different molecules used.
A liquid sample will be injected into a stream of solvent which is the mobile phase and this
will flow through a column which is packed with a separation medium, this will be known as
the stationary phase. The sample components will begin to separate from each other by the
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