MECHANISM OF HYDROPHILIC BONDING
Compounds are retained by hydrophilic sorbents through polar interactions including hydrogen bonding, pi-pi or dipole-dipole interactions. These types of interactions occur when a distribution of electrons between individual atoms in functional groups is unequal, causing negative and positive polarity. Compounds typically extracted on a hydrophilic column include analytes which have polar groups, such as amines, hydroxyls and carbonyls. Strong polar solvents, in turn, elute the analyte off of the sorbent.
These sorbents are composed of a silica backbone that is left unbonded or bonded with carbon chains containing polar functional groups. Examples of groups that have this functionality are amines, hydroxyls and carbonyls
HYDROPHILIC SORBENTS & STRUCTURES
 Sorbent                     Structure
Silica                       -SiOH
Diol                         -Si(CH2)3OCH3OHCH2OH
Cyanopropyl                 -Si(CH2)3CN
