For the analytical HPLC Vertex III column hardware KNAUER offers integrated or stand-alone precolumns. An integrated precolumn has the same inner diameter (3 mm, 4 mm, 4.6 mm) as the main column and is filled with the same material used in the main column.
It is directly integrated into the column head. We recommend integrated precolumns because you minimize the dead volume and so avoid possible peak broadening.
Stand-alone precolumns must not but can be filled with the same material and do not need to have the same diameter as the main column. They are placed in an external precolumn holder and have to be connected to the main column via capillaries. This generates a greater dead volume and might result in peak broadening.
For 2 mm ID and UHPLC columns, we recommend to use a precolumn filter. The advantage is that it has again a lower volume than a precolumn that is filled with the stationary phase.