A Sample Preparation Technique for Column Chromatography The problem of obtaining column chromatography results that approach the often superior separations routinely found in thin layer chromatography systems is often encountered in chemistry. The conventional method of applying a solid or gummy sample to a chromatography columh suffers from the fact the column should he eluted with a solvent or solvent mixture a t least as polar ss the solvent used t o dissolve the sample. This limitation often results in poor separation and streakine of the samole comoonents. W e ' h a w f m n d s ~ m p land r efferrive rnerhod ofsample preparaticm for use in column rhrornnrogmphy u,hieh rrwrnt,lr.; the appliratim r,f asample t o n thin layer chromampraphy plate, where the solidsnmple in solution icnhsorhed hy therolid phase as the solvent evaporates. Our method involves impregnating the sample t o be chromatographed on a small amount of the same material used t o make up the column. In partirular, the sample is dissolved in an appropriate solvent and about five times the sample weight of the absorbant (alumina, Silica G ete.) is added to the solution and this mixture stripped of solvent first on a rotary evaporator and then under high vacuum. The resulting dry residue can be ground to a uniform oowder in a mortar and this samole-imoreenated material olaced above the uooer sand laver that seosrates samole from " absorbant material in a conventi&al chromatography column. Elution of the column can de performld first with solvents of low polarity and firally with more polar solvents or solvent mixtures. We have used this method effectively in the separation of certain Camphenanthrenes prepared by the photofyclization of various 2-stilbazoles from the crude photolysis mixtures and in the separation of certain geometrical isomers of 2.3-disminohutane cohalt complexes. The method of impregnating a sample on ahsorbant material appears to us to be general for samples that are solids or gummy residues and seems only to be limited by the volatility of the sample.
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University of New Mexico Albuquerque, 87131
498 / Journal of Chemical Education
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Nicholas R. Beller Christopher J. Hilleary
