Chromatography is used to separate mixtures of substances into their components. All forms of chromatography work on the same principle that they all have a stationary phase (a solid or a liquid supported on a solid) and a mobile phase where liquid or a gas is involved. The mobile phase flows through the stationary phase and carries the components of the mixtures with it. Different components travel at different rates. In paper chromatography, the stationary phase is a very uniform absorbent paper. The mobile phase is suitable liquid solvent or mixture of solvents.
Experiment – 1
Aim – To understand about the separation of plant proteins using paper chromatography
My prediction – My prediction is that, by the end of the experiment, I will be able to observe the changes in the chromatography paper which we use also I will make a detailed investigation into it. I predict a successful experiment.
Equipment List –
Jar with lid - chromatography
Mortar and pestle
Chlorophyll chromatography solvent
Firstly, I had the set up my experiment with all the apparatus which was provided to me. I used a mortar and a pestle to grind to grass which was provided in order to start off my experiment. I also added some acetone to the chromatography jar to make the soft mixture and to get the liquid out of it. Suddenly, I started to see a green extraction which I poured into a test-tube. Simple filtration was the next step. So, funnel came into use along with the filter paper, I filtered the liquid into a further test tube. I had to observe carefully until all the liquid was filterized. I added chlorophyll chromatography solvent to it and then I drew a line on the chromatography paper which was provided with a pencil without placing it into the solution. After all the solution was filtered, I used a pipette to put a single drop onto the middle of the line which I drew on the chromatography paper. Then I placed the bottom of the chromatography paper into the chlorophyll chromatography solvent making sure that only tiny bit of the paper touches the water, however not drop it into the solution which was set up. [pic]
Result – After a while, I took out the chromatography paper and then realised that the dot which I drew on the middle of the line have moved itself away from the line towards the opening of the jar which suggests that my experiment was successful.
The mix of pigments in a leaf may be separated into bands of colour by the technique of paper chromatography. Chromatography involves the separation of mixtures into individual components. Chromatography means "color writing." With this technique the components of a mixture in a liquid medium are separated. The separation takes place by absorption and capillarity. The paper holds the substances by absorption; capillarity pulls the substances up the paper at different rates. Pigments are separated on the paper and show up as colored streaks. The pattern of separated components on the paper is called a chromatogram. Further identification of the pigments can be obtained by visible spectroscopy since the pigments are coloured.
High performance liquid chromatography is basically a highly improved form of column chromatography. Instead of solvent being allowed to drip through a column under gravity, it is forced through high pressures of up to 400 atmospheres. That makes it much faster. It also allows us to make a very much smaller particle size for the column packing material which gives a much greater surface for interactions between the stationery phase and the molecules flowing past it. This will allow for a better separation of the components of the mixture. The other major improvements over column chromatography concern the detection methods which can be used. These methods are highly automated and extremely sensitive....
References: CGP Chemistry AS & A2 Level
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