Roy 1. Whistler, Max Lamchen and R. M. Rowell Purdue University Lafayette, Indiana1
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A Spreader for TIC Slides
A n inexpensive and easy to construct spreader for thin layer chromatography can be made from Plexiglas sheets. This simple spreader casts uniform layers of absorbent and can be adapted to produce films of any useful thickness. Its rapid operation permits spreading a large batch of absorbent before the binder sets, and thus allows easy preparation of a number of uniform plates of high quality. The apparatus is best constructed from cut sheets, which can be glued together with the aid of chloroform. Although it could be constructed as one unit it is best made in two parts, which facilitates cleaning. Part I (Fig. 1) consists of a flat plate (A). Two long strips ( B ) of the same thickness as the slides to he prepared are glued onto A using spacers (C) of paper or plastic.
Figure 1.
The thickness of the spacers depends on the thickness of the ahsorbent layer required. The distance (X) between the parallel strips should be such as to allow the slides to move easily in and out. For easy operation the lengths (P), (Y), and (Z) (Fig. 1) should be at least three times the length of the slides. Journal paper No. 2552, Purdue Agricultural Experiment Station, Lafayette, Indiana. 1 Present address: Department of Chemistry, University of Cape Town,Cape Town, South Africa.
28 / Journol o f Chemical Education
Part I1 (Fig. 2) shows the spreader with a straight edge a t the bottom ( E ) glued on both sides to the side braces (F). Side wing plates (G) are glued to the side strips ( B ) as shown. The cross brace (H), which should be about I/,, in. above the slides when the spreader is put into position, forms a reservoir for the absorhent to he applied. Method of Spreading
A large drop of glycerol is placed on the bottom of each wing plate (G) and Part I1 is pressed down firmly onto Part I to force all the air from between the wing plates and the side strips (B). Part I1 should then be attached sufficiently to free both hands for manipulating the slides. A dry, degreased slide is put into position so that its front edge just protrudes past the scraper bar ( E ) . One or more slides should be placed behind the front one. A very thin paste of adsorbent in the appropriate solvent is poured into the reservoir (R) and the plates immediately pushed through. As the coated slides emerge they should he placed level to dry. Varying the thickness of the paste will affect the thickness of the dried absorbent layer. The consistency of the paste, however, should be free-flowing; for silica gel G a mixture of 5 g absorbent in 10 ml water gives a suitable consistency. If the absorbent contains a binder, the coating should be applied quickly before the mixture starts to set. This type of spreader has been successfully used for plates varying from microscopic slide size to 10 in. X 10 in.
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Figure 2.
