Layer Thickness and Plate Size

Some investigations of the influence of layer thickness on separation have been made [300, 678]. Most authors have chosen layers between 0.5 and 1 mm thick only occasionally have thicker layers been proposed. Slurries with lower water content and special drying procedures were then suggested to prevent formation of cracks [147, 300]. Special silica gels (P-series of Firm 88) and, recently, 20 x 20 cm pre-coated plates with 2 mm layers (Firm 88) have been developed also. 

A strip of adhesive tape (Tesafilm, Scotch tape), 1—2 cm wide, is stuck all round the outside of the plate to be able to prepare thicker layers on glass plates, using the pouring procedure. The adsorbent suspension is poured into the shallow trough thus formed. The adhesive strip can be torn off after the layer has dried. 

Plates of 20 x 20 cm or the equally handy 20 x 40 cm are mostly used as carriers for reasons of economy. Halpaap [266], however, has preferred 1 m plates and constructed a correspondingly sized V2A development chamber and other accessories. 

Various firms now offer collections of basic equipment for preparative TLC (Firms 33, 44, 129). Do it yourseff spreaders for preparative TLC have also been described [56, 147, 374]. 

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