Grafted planar chromatography

Chromatographic plates can be connected for both capillary-controlled and forced-flow planar chromatography (FFPC), i.e. irrespective of whether capillary action or forced-flow is the driving force for the separation. The first technique is denoted as grafted planar chromatography (31), while the second is known as long distance (LD) OPLC, which uses heterolayers (32, 33). 

Nowadays, almost all commercially available HPLC stationary phases are also applicable to planar chromatography. In addition to the polar hydroxyl groups present on the surface of native silica, other polar functional groups attached to the silica skeleton can also enter into adsorptive interactions with suitable sample molecules (34). Silica with hydrophilic polar ligands, such as amino, cyano, and diol functions, attached to the silica skeleton by alkyl chains, all of which have been well proven in HPLC, have also been developed for TLC (34). 

12 SERIALLY CONNECTED MULTILAYER FORCED-FLOW PLANAR CHROMATOGRAPHY 

For this technique, the upper plate has a mobile phase inlet channel on one edge and a slit at the opposite edge for directing the mobile phase toward the next plate (33). The slit (width approx. 0.1 mm) can be produced by cutting the layers with a sharp blade this enables easy passage of mobile phase and separated compounds without any mixing. The cushion of the OPLC instrument is applied to the uppermost layer only, and each plate presses on to the sorbent layer below. 

The potential of serial connection of layers can be used for multidimensional planar chromatographic separations on different stationary phases of decreasing 

---