The Mechanism of Chromatographic Retention - Retention and Exclusion > Silica Gels with Different Exclusion Properties > Page 64
The adsorbents Spherosil 10, Silarex II and Partisil 10 were used to demonstrate the basic chromatographic differences between the three groups of silica gels. Each gel was used to separate a mixture of solutes having molecular diameters of 1100Å, 240Å, 49.5Å, 27.1Å and 7.4Å respectively and the chromatograms obtained from the three silica gels is shown in figure 29.
It is seen that the large-pore silica gel, Spherosil 10, is suitable for separating substances having molecular diameters lying between 240Å and 11,000Å. Solutes having diameters less than 240Å are crowded together and unresolved.
The silica gel having an intermediate range of pore diameters , Silarex II 10 is seen to be suitable for separating solutes with molecular diameters lying between 27Å and 240Å. Little pore volume is left available for solutes to elute that have molecular diameters less than 27Å or greater then 240Å.
Spherosil 10 Silarex 2 10 Partisil 10
Column Length 50 cm, mobile phase tetrahydrofuran, Molecular diameter of solutes, (1) 11,000Å, (2) 240Å, (3) 49.5Å, (4) 27.1Å and (5) 7.4Å.
Figure 28. Chromatograms Demonstrating the Different Exclusion Properties of Three Silica Gels