For the separation, removal, isolation, purification, characterisation, identification or quantification of fibrinogen or a protein that is a fibrinogen analogue, an affinity adsorbent is used that is a compound of formula II wherein one X is N and the other is N, C-Cl or C-CN; Y is O, S or NR2; 0 Z is O, S or NR3; R2 and R3 are each H, alkyl, hydroxyalkyl, benzyl or ss-phenylethyl; n is 0 to 6; A is a support matrix, optionally linked to the triazine ring by a spacer; R7 is a group bearing a positive charge at neutral pH; W is an optional linker; V is an aromatic group; and R8 and R9 are each H, OH, alkyl, alkoxy, amino, NH2, acyloxy, acylamino, CO2H, sulphonic acid, carbamoyl, sulphamoyl, alkylsulphonyl or halogen or a cyclic structure such as a morpholino group, or R8 and R9 are linkedto form such a cyclic structure.