Could/should you reverse the flow on your LC column to regenerate?

It can be useful to reverse the flow on a dirty HPLC column. Most of the dirt is deposited at the column head and can be removed more easily when rinsing against the flow direction which means it doesn´t have to be transported along the entire column length. Furthermore, a reversed flow can help to eliminate dead volume at the column head (at least temporarily).

However, not every column can be operated with reversed flow! It is usually no problem with the classic 3 µm and 5μm silica gel columns, but – when it comes to columns with special features, e.g. < 2 µm UHPLC particles or CoreShell particles - you have to be cautious to ensure constant and consistent separation performance.

There are several reasons (manufacturing, hardware, etc.) why LC columns cannot or should not be operated against the recommended flow direction. Always ask the manufacturer in advance if the column is suitable for reversed flow or not.

Don’t forget! When rinsing columns - no matter in which direction:

• first remove the precolumn
• direct the column outlet into a waste vessel
• Start rinsing only at half flow rate to avoid sudden strong pressure increases