In this technical article you'll learn about the roles of pore size and particle size for an HPLC packing material.
In essence, these two properties of an HPLC packing are not related. Most reversed-phase HPLC columns are based on a stationary phase bonded to silica particles. These particles form the basis of the packing material. The most popular particle sizes are 5-, 3.5- and 3-μm particle diameters. Particles of <3-μm are becoming increasingly popular because of their increased column efficiency and relative independence of column efficiency on flow-rate. The pore size of HPLC particles can vary widely from product to product, but should be consistent within a particular product line of columns. There are two general categories of pore sizes. Small-pore particles have pores ranging from about 6-15 nm (60-150 Å), with the majority in the 8-12-nm range. Packings based on these particles generally are used for 'small molecule' separations, where the sample molecular weight is <≈1000 Da. Large-pore particles have pores of ≥ 30 nm (300 Å) and tend to be used more for large molecule separations, such as proteins.
By reading the full article you will learn why a particular pore size of a column is selected and what both the pore size and particle size control.
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