How does pore size of the material affect my extraction?

Sorbent-analyte interactions take place inside the pores.  The average pore size of regular polymeric and silica-based SPE material is 60-85 Å, which restricts access to molecules larger than 15kDa.  Analytes must be able to fit in the pores in order to interact with the sorbent.  Large pore sorbents are available in 260- 300 Å for molecules with molecular weights > 15 kDa.