Porous particles:

Totally porous particles have a large surface area in the range 100 to 860 m²/g with average being 400 m²/g. The mean pore diameter is inversely related to the specific surface area where small molecules enter the pores. The particles can be packed into the HPLC column of efficiencies up to 800 theoretical plates per centimeter if 5 µm particle sizes are used. However, larger particles give proportionately small number of theoretical plates whence the efficiency of separation goes down.