Pre-column filters are an inexpensive option to protect the HPLC column from debris and particulates. Particles and debris cause increased pressure on the column when buildup occurs. These filters are typically a union style connection, with an easily replaceable economic frit of specified porosity plumbed between the injector and the column.
Since pre-column filters are placed after the injector and immediately before the column, it is important to minimize swept volume (internal volume due to the holder geometry and frit porosity). High-performance pre-column filters can be used at Ultra-High Pressures, have small pore sizes (down to 0.2 µm), and have minimal internal volumes to minimize peak broadening.