A fluidized bed chromatographic process for the purification and binding of molecules in a liquid to an active substance covalently bound to chromatographic adsorbent particles. The adsorbent particles are formed of a porous composite material having pores allowing access to the interior thereof and consisting of at least two density controlling particles of low or high density, or both, and a matrix formed by consolidating at least one conglomerating agent. The density controlling particles are dispersed in the matrix. The adsorbent particles have a relative density with respect to the liquid which is less than 0.95 and greater than 1.1, and they have a particle size within the range of 50-750 .mu.m. The relative density and particle size range of the adsorbent particles are selected to provide desired floatation/sedimentation properties of the adsorbent particles in the liquid in the fluidized bed process.