Chromatography

Chromatography

1. What is it?

   • A technique for the separation of a mixture by passing it in solution in which the components move at different rates.

2. How does it work?

   • 1) Collect a piece of chromatography paper and a beaker.
     • 2) Draw a line 2cm above the bottom edge of the strip with a pencil line and ruler
       • 3) Start line must be drawn in pencil as the ink will run if a pen is used.
         • 4) Collect sample and place a small concentrated dot into the start line.
           • 5) Pour water into the beaker to 1 cm depth. The water must not go over the start line.
             • 6) The water must not go over the start line as it will wash away the sample.
               • 7) Place the chromatography paper into the water and leave it to run. the water will move up the paper and separate any colours in the sample.
                 • 8) Once there is a gap between the sample and the water level remove the chromatography paper and in pencil draw a line to show the level the water moves to. This is called the solvent front.
                   • 9) Leave to dry and calculate the RF value per color in the sample.
                     • Results
                       • A pure substance produces one spot on the chromatogram
                       • An impure substance produces two or more spots

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