PURPOSE: To separate even a compd. which is hardly separated in an alkyl group bonding-type stationary phase by using a filler obtained by allowing a specified cyclic polysiloxane to react with a porous carrier.

CONSTITUTION: A cyclic polysiloxane shown by the formula (where R1-R4 are a monovalent hydrocarbonic group, X is a halogen atom or a hydrolyzable org. group, l is an integer of 1-10, m is an integer of 0-10, l+m is an integer of ≥ 3, n is an integer of 1-20, and p is an integer of 0-2) is allowed to react with a porous carrier having an active hydrophilic group on its surface to obtain a filler which is used. A globular or crushed porous silica gel or alumina or a porous glass having an active hydrophilic group on its surface are preferably used as the porous carrier having an active hydrophilic group on its surface. As for the cyclic polysiloxane, the R1-R4 are a monovaelent hydrocarbonic group exemplified by a methyl group, and a halogen atom such as chlorine or an alkoxy group is preferably used as the X.