Abstract Methods for preparing biospecific adsorbents and immobilized enzymes utilizing Sepharose CL as a support and trichloro-s-triazine as the linking agent are described. The difficulties encountered during conventional aqueous and mixed aqueous-phase reactions of trichloro-s-triazine with insoluble polyols, particularly reagent hydrolysis, are avoided by performing the activation reactions in anhydrous organic phase and replacing the second chlorine on the triazine ring by an aromatic amine. Ligands can be coupled to the activated support in either aqueous or organic phase. The methods have been applied to the attachment of a number of different enzymes, proteins, and small-molecule ligands to Sepharose. The superiority of the triazine linkage to the cyanogen bromide linkage is demonstrated.