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The purpose of this experiment is to identify plant pigments by separation, using thin layer chromatography.

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Introduction

________________ Thin Layer Chromatography Aim: The purpose of this experiment is to identify plant pigments by separation, using thin layer chromatography. Thin Layer Chromatography Thin Layer Chromatography (TLC) is a chromatographic technique that is used to separate mixtures. It is very commonly used in synthetic chemistry for identifying compounds, determining their purity and following the progress of a reaction. One of the solids that are mostly used in chromatography is silica gel. There are many uses of thin layer chromatography which are: * To determine the number of components in a mixture. * To determine the identity of two substances. * To monitor the progress of a reaction. * To determine the effectiveness of a purification. * To determine the appropriate conditions for a column chromatographic separation. * To monitor column chromatography. Thin Layer Chromatography is a fast and a simple analytical technique. TLC involves spotting the sample to be analysed near one end of the sheet that is coated with a thin layer of an adsorbent. The sheet can be the TLC slide and this is placed on end in a covered jar containing a shallow layer of solvent. As the solvent rises by capillary action up through the adsorbent and different positioning occurs between the components of the mixture dissolved in the solvent. The more a given component of a mixture is adsorbed onto the stationary phase, the less time it will spend in the mobile phase and the more slowly it will migrate up the TLC slide. ...read more.

Middle

Nettle leaves can sting you and it may cause rashes and irritation to skin. There is a medium chance of this occurring which means a 7/10 chance of this risk. Supervisor made the nettle plant dye for everyone to avoid the risk of any hazards. An overall risk of this hazard happening is: 6/10 x 7/10 = 42/100. Handling organic matter There is a 6/10 of this potential hazard occurring as some people that are working in the lab are not likely to know the risks of handling the organic matter. Risk of infection and contamination to skin. There is a low chance of this hazard occurring which means a 3/10 chance of this risk. Wash hands thoroughly after contact with the leaves so that you can avoid any rashes and irritation to skin. Follow instructions that are given by your teacher to avoid these risks. An overall risk of this hazard happening is: 6/10 x 3/10 = 18/100. Chemical spillage There is a 9/10 chance of this potential hazard because people are more likely to spill chemicals when working with it in the lab. Risk of ingesting/come into contact with ethanol Anonymous results may occur and also if the plant dyes get on the clothes then it might damage it. There is an 8/10 chance of this hazard occurring. Wipe up any spillages that has occurred and report any damage to equipment/avoid consuming ethanol An overall risk of this hazard happening is: 9/10 x 8/10 = 72/100. ...read more.

Conclusion

To improve this, I would have wanted more time to crush and grind the leaves so that there would be more dye to put on the TLC slide. Another way of retrieving more dye is by thoroughly blending the leaves using a blender and filtering out the solution. The solution didn?t contain enough pigment and it wasn?t concentrated and this could affect the experiment as you can?t see the pigment and therefore you can?t compare it. To improve this, I would get the pigment more concentrated by evaporating the alcohol so I would get a more concentrated solution. This would increase the amount of pigments on the TLC slide. Also, using a small amount of plant gave a very faint trace and this means that it is very difficult to see all of the pigments, and so the number may be miscounted. The choice of plants could be a problem as I have only tested three plants which are grass, nettle and ivy and this is not a very good comparison because they may be other plants that would give a higher concentration of pigments. Also the method of extraction of the dye could be a problem as water and sand was used to crush all the plants properly in order to get the dye. The dye was extracted well but the water and sand can absorb light as well which can affect results. ...read more.

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