The function of a guard column is to protect the analytical column from the damage caused by particulate matter and strongly adsorbed material. To maintain an adequate capacity for sample impurities without introducing excessive peak dispersion, the volume ratio of the guard column to that of the analytical column should be in the range 1:15 to 1:25.
Ideally the packing of the guard column should be the same as the analytical column so that the chromatography of the analytical column is not altered. Sometimes a similar packing may be used for the guard column. In our catalog, the analytical columns and their suitable guard columns are listed together.