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Experiment to identify an unknown mix of amino acids using paper chromatography

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Introduction

Experiment to Identify an Unknown Mix of Amino Acids Using Paper Chromatography Aim The aim of this experiment is to attempt to identify the amino acids present in the mixture (unknown solution provided) utilising the paper chromatography technique and a small range of amino acid solutions which may or may not be present in the mixture. Introduction Chromatography - (from the Greek "chroma" - colour; and "grafein" - to write) is the collective term for a family of laboratory techniques for the separation of mixtures. There are several different types of chromatography techniques including paper, thin layer, column, gas and liquid. It involves passing a mixture dissolved in a "mobile phase" through a "stationary phase", which separates the analyte (the substance that is to be separated during chromatography) to be measured from other molecules in the mixture and allows it to be isolated. In this experiment the chromatography technique employed was Paper Chromatography. Paper Chromatography is a technique which involves placing a small dot of sample solution onto a strip of chromatography paper. ...read more.

Middle

b) The chromatograph paper was prepared by marking in pencil, an origin line approximately one half inch from the bottom of the chromatograph paper. The paper was labelled "amino acids" 1- 6 (the mix). 1 = Leucine; 2 = Arginine; 3 = Aspartic Acid; 4 = Alanine; 5 = Lysine and 6 = Unknown Mix. With the use of capillary tubes, discrete spots of each solution were placed in their designated areas on the origin line of the chromatograph paper. c) On drying, the chromatograph paper was folded to form a cylindrical shape and stapled at the top and bottom to hold it in place. This was then placed, with the origin line at the bottom, into the solvent in the chromatograph tank (carefully ensuring it did not touch the sides of the tank). A check was made to ensure that the solvent did not come above the origin line and the watchglass cover was placed back over the top of the chromatograph tank. d) The experiment was left to run for one hour. ...read more.

Conclusion

Conclusion From the results obtained the mix was determined to be a combination of two amino acids - Aspartic Acid and Leucine. This determination was made as a result of the mix displaying identical Rf values as Aspartic Acid (0.18 or 18%) and Leucine (0.76 or 76%) in their distances from the origin line. Discussion There were one or two potential errors in the procedure. Firstly the procedure/method indicated that the tank should have had 50cm3 of the solvent put in, but only 10cm3 was actually used. Presumably this change was made to allow for the origin line on the chromatograph paper utilised not to have been completely submerged from the outset. This allowed the solvent to travel up the paper past the origin line taking the amino acids with it. Secondly, the procedure also indicated that the "run" should have been for a minimum of 1.5 hours whereas in actuality it was only left to run for 1 hour. This did not appear to affect the results though, as there was clear indication of what the unknown mix was. ...read more.

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