The present invention relates to the use for affinity purification of an antibody or an fragment of an antibody, of a ligand-substituted matrix comprising a support material and at least one ligand covalently bonded to the support material, the ligand being represented by formula (I) wherein Sp is a spacer group; v is 0 or 1; Am is an amide group —NR1—C(O)—, and wherein either NR1 is attached to Ar1 and —C(O)— is attached to Ar2, or —C(O)— is attached to Ar1 and NR1 is attached to Ar2; and R1 is hydrogen or C1 to C4 alkyl, preferably hydrogen or methyl; and more preferably hydrogen; Ar1 is a divalent 5- or 6-membered substituted or unsubstituted aromatic ring; Ar2 is 5- or 6-membered heterocyclic aromatic ring which is (a) attached to a further 5- or 6-membered aromatic ring via a single bond; or (b) fused to a further 5- or 6-membered aromatic ring as part of a multicyclic ring system; or (c) attached to at least one substituent selected from C1 to C4 alkyl; C2 to C4 alkenyl; C2 to C4 alkynyl; a halogen; C1 to C4 haloalkyl; hydroxyl-substituted C1 to C4 alkyl; C1 to C4 alkoxy; hydroxyl-substituted C1 to C4 alkoxy; C1 to C4 alkylamino; C1 to C4 alkylthio; and combinations thereof.