Column Chromatography: Column Assembly

General Assembly

These diagrams display the assembled column chromatography apparatus. In the diagram at left, the layers of column packing material are labeled. Note the lower layer of glass wool that protects the stopcock valve assembly from the alumina and sand column packing material. The sand layers are each 1 cm thick. Make the alumina layer as long as possible but remember to leave the last 4-5 cm of the column open. Also note the wash bottle trap used to isolate the apparatus from the domestic water supply.

Packing the Column

Using a stirring rod, push a small wad of glass wool to the bottom of the empty column.

The glass wool prevents the sand and alumina from entering and consequently destroying the valve at the bottom of the column. Using a long stirring rod, gently pack the glasswool until it covers the hole leading to the valve

Pour sand into the column until a 1 cm layer has formed. Use a funnel to direct the sand into the column. The sand forms the foundation for the alumina layer that will be added in the next step.

Add alumina to the column until you have formed a layer approximately 10 cm tall

Use a funnel and proceed carefully. Don't overfill the column. There must be enough room for a final sand layer and empty space for the introduction of liquid samples. Avoid breathing the alumina dust.

Create another sand layer on top of the alumina and position a small, circular piece of filter paper over the sand.

The filter paper keeps the sand layer from being disturbed as liquids are poured into the top of the column.

Pack the column by GENTLY holding an engraving tool up alongside the side of the column.

The vibrations will accelerate settling of the column contents. (ie. some settling may occur during shipping). If the column is not properly packed, open spaces or gaps in the alumina will develop as solvents are introduced in subsequent steps