The present invention relates to a chromatographic adsorbent for selectively adsorbing IgG, comprising the following formula ##STR00001## and its corresponding enol-form, wherein X represents O, S, or NH; R.sup.1 represents H, C.sub.1-6 alkyl, C.sub.1-6 alkoxy, C.sub.1-6 alkoxy-C.sub.1-6 alkyl, Ar, --C(O)NHR.sup.3, --C(O)--R.sup.3 or halo; R.sup.2 represents H, C.sub.1-3 alkyl or halo; R.sup.3 represents H, C.sub.1-6 alkyl, C.sub.1-6 alkoxy, C.sub.1-6 alkoxy-C.sub.1-6 alkyl or Ar; n represents 0, 1, 2 or 3; Y represents a carrier. The present invention also relates to a method of producing said adsorbent as well as use thereof for separating substances by affinity chromatography.