Abstract: A modified solid carrier is used to covalently immobilize biomolecules such as proteins. The carrier is based on well-known matrix materials modified to have covalently bound functional groups of formula I ##STR1## that are suitable for covalent immobilization, where A is a spacer group; X is O, S, or NH and n is 0 or 1. The modified solid carrier is prepared by reacting ammonia with glycidyl groups of a carrier to form .alpha.-hydroxy-.beta.-amino groups, reacting these groups with 2,4,6-trichloro-s-triazine to form an N-triazinyl group-containing carrier, reacting this carrier with ammonia and reacting the resultant carrier with 2,4,6-trichloro-s-triazine.