A small amount of a reddish colored liquid is added to the top of a chromatography column. Within 5 minutes two bands become apparent. The space between the two bands increases over time. The first band leaves the column after about 10-15 minutes and the second band leaves after about 20 minutes. The beads of gel in the column contain pores.
Smaller molecules diffuse into the gel pores and therefore flow through the column at a slower rate.
Larger molecules do not enter the pores and flow through the space around the beads and thus pass through the column at a faster rate. This type of chromatography is used for desalting as well as fractionation. There should be a larger cap for the top with two smaller caps one for the bottom of the column and one that attaches to the larger cap for the top. Attach syringe needles to top and bottom of column along with the teflon tubing. Use one Erlenmeyer to catch the flow from the bottom of the column.