Procedures to Expedite Column Chromatographic Separations Recentlv it was nerrqsary to perform column rhromatographir separation of the rompmenti d a solid residue from a drlute xolutim. It was found that if s small amount of the c h m n packing material was added t u the flnsk prwr 111 the ewpornrion of the solvent, t he residue and column packmg formed a mixture which did nut ndhera r#, the wallsof the flask. he granular mixture could be added to the top of the column conveniently. Since the matrix was column packing, no extraneous material was introdueed into the column by this procedure. A typical experiment is described. I t was desired t o cheek the purity of a sample of kiton red S (a dye) which was in dilute solution (IOW M )in ethanol. Approxim'ately 3.7 g Silica Gel (28-200mesh) were added to a 50-ml sample of the dye solution. The ethanol was evaporated on a rotary evaporator. The free-flowing residue did not adhere to the walls of the flask. It was calculated that the residue contained 2.9 mg of the dye. A 2.3-g sample of the residue (containing 1.8 mg dye) was then placed on tap of a column of Silica Gel (40 g) in a %-in. i.d. glass column. The Silica Gel-dye mixture was simply sprinkled on the top of the column through a funnel while thecolumn was tapped gently toensure that the material settled evenly. The column was then eluted, solvent evaporated, and recovery of dye determined. A 95% recovery was achieved. During the elution process it was found that a convenient method for safely pressurizing the column to a pressure slightly above ambient was to attach a small, inflated inner tube (of a size appropriate for a power mower tire) to the apparatus. Prior to inflation, the one-way valve in the tire was removed and the tube was attached hy means of rubber tubing to a stopcock. This arrangement allowed the tube t o retain its pressure during attachment t o the column. Inflation of the tube was easily accomplished by means of a n air pump. A pressure equalizing funnel was used to simultaneously pressurize the column and the elution solvent reservoir. While i t is recognized that many other types of systems (balloons, etc.) are used commonly t o obtain small positive pressures, the inner tube has the advantages of providing a higher over-pressure than a balloon, a larger "pressure reservoir" than a simple bulb, and complete safety a t a nominal cost. Department of Aero-Mechanioal Engineering Air Force Institute of Technology Wright-Patterson Air Fbrce Base, Ohio 45433
564 / Joumai of Chemical Education
Ernest A. Dorko William W. Baker
