Extraction tests of blood biomolecules such as glucose, urea and triglycerides are carried out by simple contact of plasma with porous silica samples. Amorphous silica materials are prepared from a sol-gel method using a nonionic surfactant molecule as an organic source and silica source in a strongly acid medium. The porous texture of the solids allows the trapping of biomolecules and significantly reduces their concentration in blood by simple prolonged contact. Adsorption is therefore an efficient method that leads to blood purification when the concentration of biomolecules is very high in the blood.