Characterization of the mechanical properties of polymeric chromatographic particles by micromanipulation.

Chromatographic particles should not possess only desirable surface chemical properties but also mechanical properties. The latter determine the deformation of the particles under hydrodynamic conditions of packed beds and further the pressure drop. Understanding the mechanical properties of chromatographic particles is essential to successful design and operation of such processing equipment. The mechanical properties of single chromatographic particles made of different formulations and with different surface modifications were characterized by a novel micromanipulation technique. The principle of this technique is to compress single particles between two parallel surfaces. The force being imposed on the particles and their deformation under compression are measured simultaneously. The particles range from 30 to 300 microm, depending on their formulation. 10-30 particles from each sample were compressed up to a particle deformation of 70% in order to get statistically representative data. Particles for hydrophobic interaction chromatography were proved more stable than resins for ion exchange or gel filtration. The difference is remarkable in dry state and is less in wet state. Water seems to "level out" the differences in mechanical stability of resins. The stability seems to be also dependent on the speed of water release out of the resins.