Estimated Time 30 minutes
Radial chromatography is a technique used to separate mixture of compounds. It is composed by a stationary phase which is normally a silica gel, aluminum oxide or cellulose immobilized in a circular plate. A liquid phase which is the solvent that moves the compound by the stationary phase. Radial chromatography uses the centrifuge force to display the solvent and the compound from the center to the end of the plate by separation the composition of the mixture of compounds.
Radial chromatography is one of the most important separations on chemical research. The construction of the plates play and important role on the separation besides that the thickness of its can be determined by the amount of material used to cover the plate surface. On this activity the students should be able to clean and build a new radial plate.
- Silica Gel
- Radial Chromatography Instrument
- Mixtures to Separate
- Calsium Sufate
- Soap and water
- A piece of felt
Building your Own Plate for Radial Chromatography
1. Remove the old stationary phase from the radial plate, collecting the old stationary phase in a labeled waste bottle (don't breath the dust).
2. Wash and scrub the radial plate by using soap and let it dry in the oven.
3. Let it dry at room temperature.
4. Weight the materials to make the mixture to form the new stationary phase film using next table:
5. Mix the materials in a beaker and stir the mixture. NOTE: The next steps must be completed within 5 min since the mixture will begin to set within 5-10 min.
6. Turn the plate slowly by the central rod and pour the mixture in a continuous stream in overlapping circles close to the central metal disk. Keep the beaker close to the rotor to minimize the formation of separate drops of the mixture. Slight agitation will encourage thick mixtures to flow. Touch the mouth of the beaker to the metal disk of the arbor to remove the last hanging drop.
7. Grip the center of the rod of the arbor and raise the rotor about 1 cm then lower, bumping the handle below the rotor against the felt (or cloth) covered surface. Do not turn during the dumping. Repeat about 5 times. Bumping liquefies the mixture releasing air bubbles, allowing gravity to spread the mixture and smooth out inhomogeneous parts.
8. Cover the rotor with a bowl or cardboard box for an hour and then put it into the oven overnight.
9. Remove the excess of silica gel from the Radial Chromatography Plate with the right knife (1, 2 or 4mm) depending the amount of materials used. The plate is ready to be use it.
1. How many materials were used to cover the plate surface?
2. What is the importance of the calcium sulfate?
3. Why is so important to clean and dry perfectly the plate before to place the new material?