Porous layer beads:

A porous or pellicular layer bead type packing material consists of a solid, spherical along with an average particle diameter 30-40 µm coated along with a thin porous outer shell, classically of 1-3 µm thick. It might be a silica gel layer, a network of small spherical particles bonded to the solid core. It might also be monomeric or polymeric organic phase. Surface areas of the porous layer beads range from 5 to 15 m²/g. These materials are simple to be packed because of its dense core but suffer from limited sample capacity due to small surface areas. Porous layer packings exhibit good efficiency since of improved mass transfer within the stationary phase. Longer columns are probable since the pressure drop is lower due to larger particle size of porous layer supports. Thicker coatings give rise to slower mass transfer but have increased sample capacity.