When chromatographic separation is done in a normal phase mode, the surface chemistry of the stationary phase has a polar characteristic. The mobile phase is generally nonpolar organic solvent (such as hexane or heptane). Because of the limited exibility in variation of the mobile phase polarity and functional stationary phase, separation in normal phase mode has not grown as much as reversed- phase mode. However, continuous advancement in surface modi cation has rejuvenated interest in normal phase chromatography. Furthermore, there are some separations that are achieved more conveniently using normal mode.
Silica, alumina, polymers, and a few other metal oxides are the most favorite substrates for normal phase separation. The important features include high surface area, availability in high purity, and homogeneous functional groups.