Packing a Chromatography Column

1. Solvent system

Use thin layer chromatography to determine the proper solvent system for column chromatography.

A good solvent system for column chromatography is one which in TLC gives an Rf of approx. 0.3 for the major component of the system.

2. Solid support

TLC is also used to determine the proper solid support to use for the separation.

The amount of adsorbent used should be equal to approximately 20 times by weight the amount os solid to be chromatographed.

Steps in Packing a Column

1. Place a small wad of glass wool in the bottom of the chromatography column. A thick enough wad to prevent the passage of solid support but not too thick that a large amount of air is trapped.
2. Fill the column three-fourths full of eluting solvent and drain a small amount from the column. To remove any air bubbles from the glass wool, tamp it with a glass rod. Note:The glass wool must be free of air bubbles before you continue!
3. Using the powder funnel, add a thin layer of sand on top of the glass wool.
4. Prepare a slurry of solid support (alumina or silica gel) by mixing it with some eluent.
5. Drain some of the eluent through the column, then slowly add the slurry of solid support.

Hints to Packing a Column:

* Sometimes drain small amounts of eluent from the column.
* Tap the column with a piece of pressure tubing to help the solid support settle.
* The column support must be packed gently until it no longer settles.
* The final column of solid support should be 10 to 15 times as tall as it is as wide.
* Warning! Never drain out solvent to the extent that the surface of the solid support is exposed.
* A small layer of sand is normally placed on top of the solid support to protect the surface. It too must be below the surface of the eluting solvent.