A procedure for the quantitative determination of interactions of ligands with receptors adsorbed or immobilized on the surface of a solid material which can be functionalized, transparent and with low refractive index, by direct measure of the reflection of light. The procedure includes utilizing a planar surface, flat or rough, of a transparent solid material formed from a hydrophobic amorphous polymer, having a refractive index between 1.3200 and 1.3500, which is brought into a solution of a mixture containing from 1 nanogram/ml to 10 milligrams/ml in concentration of molecules with a function of receptor or reagent.