Classification of Chromatographic Methods Chromatographic methods are of two basic types. In column chromatography, the stationary phase is held in a narrow tube, and the mobile phase is forced through the tube under pressure or by gravity. In planar chromatography, the stationary phase is supported on a flat plate or in the pores of a paper, and the mobile phase moves through the stationary phase by capillary action or under the influence of gravity. We consider here only column chromatography. Planar chromatography is discussed in Section 34B.