CoachIn gas chromatography (GC), the mobile phase is a gas (helium, hydrogen or nitrogen) and the stationary phase a liquid film coating the inside of a long capillary column, kept in an oven. In high-performance liquid chromatography (HPLC), a pump pushes a liquid mobile phase through a short column packed with small particles. In reversed phase HPLC, the stationary phase is nonpolar (silica carrying long alkyl chains) and the mobile phase a polar mixture of water with methanol or acetonitrile. In gradient elution, the composition of the mobile phase is changed during the run, in liquid chromatography, to elute strongly retained compounds faster.
