Selection of the Stationary Phase Some Help from an

7 SELECTION OF THE STATIONARY PHASE SOME HELP FROM AN UNDERSTANDING OF THE PROCESS OF SEPARATION 

While the selection of a stationary phase to be used in the analytical column may appear complex, the decision can be greatly simplified by considering the three basic methods of separation currently in use. These are gel filtration or size-exclusion separation, reversed-phase or hydrophobic separation, and ion-exchange separation. In general, each type of separation uses a different kind of packing material, and since each type of separation exploits a different property of the molecules, the choice of packing really comes down to which property of the molecules would be most useful in achieving the separation. 

For example, to use size-exclusion chromatography, the compounds to be separated must differ in size, shape, or both, while to use solubility or charge, the compounds must differ in polarity or net charge, respectively (Table 2.2). 

While deciding on a stationary phase using these as the only criteria clearly represents an oversimplification, and the reader is referred to specific works for more details, this approach can go a long way toward facilitating the selection of the analytical column. 

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