What are the two common approaches used in column chromatography?

The two common approaches used in column chromatography are the dry packing approach and the wet packing approach to filling a chromatography column.

• Dry Packing Approach: In the dry packing approach, the column is first filled with a dry solid phase. The mobile phase is then added and flushed through the column until it is completely wet. From here on, the column is never allowed to dry.
• Wet Packing Approach: In the wet packing approach,  the liquid and solid are mixed outside of the column and the solution is then carefully poured into the column. Wet packing is generally the preferred approach in most instances because it uses up less liquid and is overall faster than the dry packing approach. Regardless of which approach is used to fill the column, two things to make sure are that the stationary bed is even and there are no bubbles.