Abstract: A solid phase can be coated superficially with a polymeric coating by substituting immobilized metal ions on the surface of the solid phase with a hydrophilic polymer or a derivative or aggregate thereof, through a chemisorption process. The solid phase may comprise a magnetic material, such as magnetite, and may have a particle form. The coating can be produced by bringing the solid phase into contact with a solution of a reagent which includes at least one metal chelating and one reactive group, and subsequently bringing the solid phase into contact with a solution of a compound which reacts with the chelater reagent adsorbed on the solid phase. The polymer layer may constitute a polyhydric alcohol, a polyamine, or a polyamide, for example a polysaccharide, such as agarose, a protein or a peptide, a polyacryl amide, etc. and the reactive group may be a vinylsulphone or an epoxide, an aminothiol or a hydroxyl.