Pore structure, size and surface area

The pore structure and size is critical for efficient chromatography and this is borne out by the fact that many supports of identical particle size, and nominally of similar pore size, often display different characteristics. As discussed in Chapter 2, van Deemter s theory suggests that the most critical attribute of a stationary phase is the ease of mass transfer through the pores of the particle. 

The control of pore size and structure during preparation is a complex process that has been mastered by few manufacturers, but it is true to say that pore size distribution and uniformity is more readily achieved in silica particles than it is in polymeries. This is not to say that polymeries are inferior, because in contrast these stationary phases have a more uniform particle size. 

The branches of an Oak are more diverse than those of a Spruce  

In practice, the less efficient mass transfer within polymeric stationary phases results in a lower optimum flow rate being obtained following a van Deemter plot. It is essential that the 

At first glance the specifications of many stationary phases in a particular mode of separation may appear to be the same. For example, in reversed phase chromatography there are many C18 based media that will have the same carbon load, the same pore size distribution, and so on. However, stationary phases from different manufacturers will behave differently, so it is important 

---