The precolumn is most beneficial when placed before the separation column. This placement works most efficiently to remove contaminants from both the mobile phase and the sample.  However, an adequate packing material has yet to be identified for the CAX and PP-ODS separation columns and in this case the precolumn should be put in front of the injector to clean the mobile phase.  Additionally, the CAX and PP-ODS methods are used only with microdialysis samples which are much cleaner than other types of samples and therefore require less cleaning. 

Regardless of types of columns, there is an option to put a precolumn before the injector and not before the separation column for microdialysis samples. This precolumn configration has the advantage that the precolumn will not affect the peak resolution, but apparently does not work to protect the separation columns.  If you prefer keep the system simple and avoid factors which may become troublesome, this non precolumn but preinjector precolumn configration may work. Please understand the column life may be a little bit shorter. Please use a 4 mm precolumn for a bigger capacity with either CA-ODS or AC-ODS .

Table. Use specific packing material and size of precolumn for each type of separation column.

If you want to eliminate the time to repack, we offer prepacked precolumns shown below.