Wide Pore Columns

So-called wide pore columns are one type of commercially available reversed phase column. As mentioned previously, pore size in a general reversed phase column is approximately 90 to 120 Å. In contrast, there are columns (hereinafter referred to as wide pore columns) with a larger pore size than usual, on the order of 200 to 1,000 Å.

Wide pore columns tend to have weaker retention for low molecular weight hydrophobic compounds compared to columns with typical pore size for the same functional group. On the other hand, wide pore columns are characterized by stronger retention for larger molecules such as peptides and proteins. This separation behavior is thought to be influenced by a size exclusion effect, where compounds that can penetrate the pores exhibit stronger retention, while those that cannot pernetrate show weaker retention. Retention of compounds also occurs within the pores, necessitating a pore size that allows the compounds to penetrate.

Diagrams of the Pores in a General Column and a Wide Pore Column

Fig.2 shows the results of peptide analysis with different molecular weights using the Shim-pack Scepter C18-120 (pore size: 120 Å), the Shim-pack Scepter C18-300 (pore size: 300 Å), and the Shim-pack Scepter C4-300 (pore size: 300 Å).

 

The retention time of Leusin-Enkephalin, with a molecular weight of around 500, is weaker in wide pore columns such as Scepter C4-300 and Scepter C18-300 compared to a typical column like Scepter C18-120. On the other hand, mid-sized molecules like Ribonuclease A and Insulin showed stronger retention and improved separation in wide pore columns like Scepter C4-300 and Scepter C18-300 compared to the typical column, Scepter C18-120.