Selection of Pore Size and Separation Range

The highest efficiency for a separation is determined by the lowest slope of the calibration curve. 

Discussing pore size selection of columns leads directly to the issue of whether to use single-porosity columns or so-called linear or mixed-bed columns, which contain mixtures of different pore sizes in a single column. Both types of columns have advantages and disadvantages [2], as shown in Table 5. 

An example may show how the different concepts come into effect in a real-life laboratory environment. This example is based on column selections many laboratories use for ordinary, general purpose work. 

Mixed-bed Fast (screening work) universal Low efficiency 

The performances of column sets (Al) and (B) are similar column set (B) is, however, more expensive. Using a specially selected column set for oligomer separation (as in column set A2), the user obtains much improved resolution and a separation range that corresponds directly to the samples under investigation. In the case of mixed-bed columns, the separation range is determined by the column and not by the application or the user, and therefore flexibility is sacrificed. This can easily be seen in Fig. 5. 

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