SEC Separation of Polysaccharides Using Macroporous Spherical Silica Gel as a Stationary Phase

Meso- and macroporous spherical silica gels of pore sizes in the range of 60-1000 Å and 40-75 µm particle size were investigated as a stationary phase for the separation and purification of polysaccharides and poly(ethylene glycols) (PEGs) of various MWs using an aqueous mobile phase. Sephadex and Bio-Gel were used for comparison as the most common stationary phases for similar purposes. The separation of dextrans of a mean MW = 31 kDa from small molecules (NaCl) was possible with SiO₂ with a pore size of 60-300 Å, but the observed efficiencies of a column of the same size were lower comparing with Sephadex or Bio-Gel. In the case of oxidized alginic acid only SiO₂ of the 60 Å pore size was suitable, while Sephadex, Bio-Gel and other investigated silicas were not efficient. Sephadex and 300-1000 Å SiO₂ offered the possibility of dividing dextrans with MW within the range of 1 MDa-10 kDa into fractions of various MWs, while Bio-Gel and 60 Å SiO₂ were not suitable. The investigated silica gels strongly adsorbed PEGs of MW 2-20 kDa. The amount adsorbed decreased with the increase of pore size and they were not useful as a stationary phase for this class of polymers. An advantage of SiO₂ of the investigated particle size was a very low back pressure comparing with Sephadex. A considerably lower price of silica offers time- and cost-efficient separation of polysaccharides.