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Unit 19 - Practical Chemical Analysis Assignment 4 & 5 (Practical Write-Ups)
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- PEARSON (PEARSON)
These are the practical write ups in relation to experiments conducted in class. This achieved the criteria.
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Unit 19 – ChemistryAssignment 4 & 5
Over a period of two weeks (09/03/2020 – 16/03/2020) Level 3 BTEC Applied Science (Forensic Science) Group
B students carried out two separate chemistry practicals regarding chromatography. The first practical I carried
out alongside Bethan Williams was the Chromatographic Separation of Amino Acids on 9th March 2020.
Chromatographic Separation of Amino Acids.
Aim
The aim of this experiment is to use paper chromatography for the separation and identification of individual
amino acids.
Introduction
Paper chromatography can be described as a useful technique for separating amino acids. The issue with the
determination and identification of amino acids within mixtures are the stimulant for the development of
modern paper chromatography. Since its discovery and application to amino acid studies, paper
chromatography has actually revolutionised the investigation of not only protein structure but also
biochemistry overall. Amino acid analysis is invaluable in the study of metabolism, the examination of enzyme
reactions as well as the determination of characteristic abnormal patterns located in urine and blood regarding
certain diseases.
Safety & Hazards
To ensure an individual is safe throughout this practical there are control measures which have been sternly
put in place and must be followed, these control measures are as follows;
A laboratory coat and safety goggles are mandatory to be worn by an individual during this practical,
to ensure no hazardous substances encounter the skin. A laboratory coat and safety goggles also are
enough to take account of the most hazards as well as risks deemed significant.
It’s important that immediately after use waste is placed in labelled containers, where waste can then
be correctly disposed of by a scientific technician.
A good laboratory practice is remined of for a safe working environment to be maintained.
Harmful/Irritant(s) -
Ninhydrin.
Ammonia.
Ethanol.
DL-Lysine .
DL-Leucine.
DL-Aspartic Acid.
Method
1. Firstly, the mobile phase needs to be made. This is created in the ratio of;
Butan-2-ol : Acetic Acid : Deionised Water
60% : 15% : 25%
However, only 20cm 3 of solution is required so the ratios needed to be in correspondence with the
solution measurements, by carrying out the following calculations this was able to be established;
Butan-2-ol : 60% x 2 = 120 ÷ 10 = 12cm
Acetic Acid : 15% x 2 = 30 ÷ 10 = 3cm
Deionised water: 25% x 2 = 50 ÷ 10 = 5cm
Then using a pipette, the above amounts of the three solutions individually need to be pipetted into a
measuring cylinder and accurately measured out (ensuring that the meniscus is on the line) before being
placed into a 1-litre glass beaker. Once all three of the solutions have been placed into the 1-litre glass beaker
a glass lid needs to be placed over the beaker. The reason why this is done first, and the lid placed over the
beaker is so that the solvent can equilibrate. Equilibrium is described as the state of balance or a stable
situation whereby opposing forces cancel each other out and no changes are taking place.
2. Whilst the solvents are equilibrating the paper slide needs to be prepared. Gloves must be worn when
handling the paper as fingerprints can be an issue on the paper during the later stages, as the amino
acids from the skin can contaminate the paper and affect the amino acids which were using, thus,
affecting our results. The paper used must be 10cm in width and 30cm in length. The paper needs to
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