Abstract: A frit (44) includes a porous support structure having a plurality of void spaces, where a plurality of secondary particles (46) are filled in the void spaces, the secondary particles (46) being dimensioned with respect to the void spaces such that the frit (44) retains packing materials with diameters of less than about 2.5 microns. Preferably one or more frits (44) are received in a high pressure liquid chromatography (HPLC) chromatographic column, where the column includes fittings and filter assemblies for receiving frits (44) at its inlet and outlet. The frit (44) can be constructed from a porous support structure with void spaces or pores that are filled with secondary particles (46) smaller those used to manufacture the support. The particles (46) contained in the void spaces are large enough to be retained by the support, but small enough to create a finer network of interconnected channels within the support's void spaces that are capable of retaining sub-2.5 micrometer particles.