Separation of Amino Acids by Paper Chromatography
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Separation of Amino Acids by Paper Chromatography Date:13/5/2011 Result: Amino acids Distance travelled /cm Rf = Distance travelled by amino acid / Distance traveled by solvent by solvent by amino acid Gyleine 7.4 3.2 0.405 Tyrosine 7.4 2.7 0.365 Leucine 7.4 5.1 0.689 Aspartic acid 7.4 2.2 0.297 Unknown B 7.4 3.3 0.446 Discussion: The solute is colourless such as amino acid, it can be located by spraying the ninhydrin solution to form a coloured spot. The colour of the complex formed between ninhydrin and aspartic acid is deep blue while that of other four are purple. Assumptions 1. Assume that the small area with concentrated spot of amino acid should be applied to obtain a deeper colour of spots.
Errors 1. The origin line should not marked by the ball pen, since the ink will dissolve in the developing solvent and the line fades gradually or even an additional spot can be observed. 2. Ninhydrin solution should not spray too much on paper since it will blur and spreads the coloured spots. It's because the solvent that are used to dissolve ninhydrin can also dissolve amino acids. 3. There are some secretion on our fingers, for example amino acids and grease. It may result in the unexpected colour zone appears on chromatographic paper after spraying ninhydrin solution. 4. The shape of chromatographic paper may not exactly be the square-shaped, so that one side of the paper may be lifted and the speed of the solvent travel in one side is faster.
2. Wear the gloves are necessary during the experiment in order to prevent the grease or amino acids on our fingers will contaminate the chromatographic paper and affect the accuracy of the experiment. 3. Use the smoothest side to be the starting point to ensure the solvent travel in on average. 4. Repeat the step of placing a small amount of amino acids in paper more than 10 times to make sure the spots will be present for good visual observation when the paper is developed. Conclusion: The paper chromatography did show that the unknown B could be defined to aspartic acid and tyrosine. By the chromatographic paper, the unknown B contains both deep blue and purple colour, and it matches the deep blue of aspartic acid. And the shape of the unknown B is teeth-shape, which is same as the tyrosine. So, the unknown B is made of aspartic acid and tyrosine.
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