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Chromatography experiment.

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20/10/01 Chromatography Experiment by Emma Walters Aim: To identify different unknown amino acids, within given substances. Apparatus: List 1 List 2 * 2 test tubes * Test tube rack * 2 bungs * 2 pins * 5 known amino acids: * Proline * Leucine * Lycine * Asparagine * Arginine * 1 unknown amino acid * Paper Chromatography * Paper Solvent * Pencil * Ruler * Tweezers * Paper Towel * Pipette * Ninhydrin * Incubator * Scissors * 1 Jam Jar * Treated Orange Juice * Untreated Orange Juice * TLC * TLC Solvent * Pencil * Ruler * Tweezers * Pipette * Paper Towel * Ninhydrin * Incubator Diagram 1: Diagram 2: Method (Part 1): * Cut 2 strips of paper chromatography using tweezers and scissors while resting on paper towel * Measure 1cm from bottom of strip and draw a line across * Draw a cross in the centre of this line * Attach a pin to the top of the chromatography paper, and put pin in bung * Place inside test tube, and measure 5mm from where the bottom of the paper lies, draw a line across the test tube * Do the same with both strips * On the cross put 10 drops of a known amino acid, wait for each drop to dry in between * On other ...read more.


The untreated Orange Juice seemed to have four unknown amino acids, my results tell me that these were Asparagine, Lycine, Arginine and Leucine. I could tell this as I matched up the Rf values with the ones that seemed to be the closest match. I know that these results were not that accurate as I know the Rf values for four of them. For Proline the real Rf value is 0.48, but our class results got 0.76 and 0.87 with an average of 0.82. This is clearly wrong. Therefore anything that I have predicted to have Proline in, might not have it in. For Leucine the real Rf value is 0.73, and our class results are 0.79 and 0.59 with an average of 0.69. This is a very close result, so it is quite accurate. So it is likely that if I have predicted it to have Leucine in it, it probably does. For Lycine the real Rf value is 0.14, and our class values are 0.41 and 0.45, with and average of 0.43. This is not a very good match. From this I can tell that anything I have said to have Lycine in it, probably does not have it in. For Arginine the real Rf value is 0.2, and we only have one class result for that and it is 0.53 which is clearly wrong. ...read more.


Another way could be putting too much TLC or Paper solvent into the jar or test tube, thus emerging the dot, making more inaccuracies. If the paper chromatography had been touching the side of the test tube while the solvent was working its way up, then this would have made our results inaccurate as well. All of these errors would make our results inaccurate and less reliable. One way of making our results more accurate would be to get rid of all these errors, which is very difficult as there are so many errors that could be made during this experiment. If I were to do this experiment again, I would start by wearing some rubber gloves, so that if I did touch the paper it would not matter as much. The second thing I would change would to be more accurate when putting the dots on the paper or TLC, making sure that they are dry properly, and that they do not spread too far. Another improvement I would make would be to make sure the paper was not touching the side of the tube, to not move the tube once the paper is in, and to make sure I draw my lines as accurate as I can. Also when I measure them, I will be more precise so that my results will be a lot more accurate then they were this time round. ...read more.

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