DNA, either native or denatured, can be immobilized by complexing with chitosan. The DNA-chitosan, which is insoluble in aqueous media, contains DNA at about 50% in weight. The DNA in the complex is accessible by enzymes and reagents. Carcinogenic heterocyclic amines, having affinity to DNA, can be adsorbed to the DNA-chitosan. The DNA-chitosan complex can be homogeneously dispersed in celite powder, and the resultant DNA-chitosan-celite is a material suitable to construct an immobilized DNA-column. The column was shown to be effective in concentrating heterocyclic amines.