A Simple Method for Preparing Replicas of Chromatograms RENJAMIN F. STIMMEL Rees-Stealy Medical Research F w d , Ltd., Snn Diego, Colifornio
Strain' hascalled attention tothe fact thata chromatogram usually does not constitute a permanent record since the colors gradually become diffuse and indistinct after the flow of solvent through the column has ceased. For permanent exhibits, teaching purposes, etc., he suggested that replicas of chromatograms might be made by packing the columns with mixtures of stable dry pigments and siliceous earth. We have found the following simple method for preparing such permanent replicas very satisfactory. The materials are readily obtainable and the replica is easily and quickly assembled. A few shavings from a Crayola crayon2 of the desired color are added to 5 ml. of benzene in a small test tube (12 X 100 mm.) which is shaken until no more crayon goes into solution. The clear solution -
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is decanted into a similar test tube and 3 to 4 g. of pure talc are added. After thorough stimng and shaking, the solid phase is thrown down by slow centrifugation. The liquid phase is decanted and the test tube placed in a drying oven a t 80' to 100° until the contents become dry. The dry cake is then broken up with a small spatula and the colored powder is added to the column a t the desired point and tamped gently until a sharp leading boundary is obtained. In order to simulate the diffuse nature of most trailing boundaries8 the colored powder is successively diluted with increasing amounts of pure talc. If a sufficient number of dilutions of the colored powder are made, a graduation in color of the bands similar to that observed in real chromatograms is achieved. For our chromatographic replica, we interspersed such colored zones on a column of anbvdrous alumina. Ind.
*-IN, "Chromatographic adsorption analysis," Eng. Chem. (Anal. Ed.),14,245-9 (1942). Crayola (school crayons) manufactured by Binney & Smith, New York City.
'The author wishes to thank the reviewer, Dr. H. H. Strain, for this helpful suggestion for achieving a more faithful replica of the trailing boundary.
