It consists of a stationary phase ( a solid ) and a mobile phase ( a liquid or a gas ) . The mobile phase flows through the stationary phase .
Methods in which the stationary phase is more polar than the mobile phase ( e.g. toluene as the mobile phase , silica as the stationary phase ) are termed normal phase liquid chromatography ( NPLC ) and the opposite ( e.g. water-methanol mixture as the mobile phase and C18 = octadecylsilyl as the stationary phase ) is termed reversed phase liquid chromatography ( RPLC ) .