Joseph M. Walsh
College of Santa Fe Santa Fe, New Mexico 87501
A Simple, Inexpensive Applicator for Preparative TLC
smoothly and rapidly pressed down over the capillary The const,ruction of a simple practical tubes and spacers which then can be picked up as a applicator for preparative thin layer chromatography is single evenly lined-up unit and which can then simply presented in this short article. In the course of sepahe attached to a piece of cardboard or plastic sheet of rating lichenic acids from an acetone fraction of the desired size and shape. The capillary tubes should Cladonia leporina, preparative tlc on talc seemed a project at least in. below the cardboard or plastic practical solution. Budget considerations ruled out holder; and the upper ends of the tubes should be left t,he commercial streak applicators, so the sample was open, not covered by tape, otherwise capillary action first applied using a 20-rl disposable pipet. An underwould bc significantly affected. graduate assist.ant, Mr. Edgar Re116 Castaileda, sugA practical vessel for holding the sample is a combusgested using three or four pipets held in a parallel row to tion boat, as illustrated (8-21865, E. H. Sargent & Co., speed up applicat,ion of the sample. After several Denver, Colo.). simplifying modifications, the arrangement later deMuch more economically, a piece of somewhat heavy scribed was arrived at. aluminum foil can be easily fashioned to make a long A rapid literature survey of two journals (J. Chvonzatogv., Vol. 1 , 1958, to the end of 1969, and JOURNAL narrow boat for holding the sample. Melting point tubing could just as easily serve for the pipets, though OF CHEMICAL EDUCATION, from 1950 to the end of 1969) the hemolytic tubing served our purposes better, berevealed that a number of different mays of applying the cause on the average, each pipet held about 10 PI. sample have been described. More than a dozen inIn operation a "14-pipet'' applicator deposited 8 ml volved the use of traveling syringes with motorized conof sample in 9 min (acetone was the solvent). Using trols. One method consisted in adding a slurry of samtlie single pipet approach, about an hour would have ple and adsorbent to a channel cut into the adsorbent been required as a rapid operator can apply about 0.12 layer.' Another2 used multiple pipets held in a speml in 1 min. For a given capillary diameter the width cially macliined jig supported on a moveable stand. of the applied sample depends on the solvent and on the The applicator described in the present article requires adsorbent. Talc, an economical support for some preno machining and can be assembled in minutes a t a cost parative tlc separation^,^ is a very soft adsorbent,, and of less than $.20. with acetone as sample solvent, the sample band rarely The only materials required are a piece of cardboard was wider than S mm. or plastic sheet in. in thickness), some capillary tubes, used for hemolytic grouping and typing (1.2-1.4 X 75 mm, Propper Mfg, Co. Inc; Long Island City, N. Y.), and some transparent plastic tape. The capillary tubes are first fire polished, then squared by aligning some of them against a block of wood that is firmly held down. The tubes are held together by two pieces of tape, so arranged that a carborundum crystal or small diamond wheel can make a cut about one-third from one of the ends. A sligbt amount of pressure is then sufficientto separate the cut capillary tubes. Thc fire polisl~edends of the larger pieces of the capillary tubes are then aligned against the block of vood with the smaller pieces of the tubing acting as spacers, in the fashion shown in the illustration. A piece of masking tape, the adhesive side facing upwards, has just the right degree of tackiness to hold the tubes, yet permits adjustment to a perfectly square arrangement. From 8 to 15 capillary tubes can be adequately squared off in a short time. Then a piece of Scotch tape can be
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TI:I:GABDI:N, U. M., J . Ch~ornalogr.,41,
~XORGIN, M. G., J . chroma tog^., 9, 379 (1962). W a ~ wJ., Rl., J. CHXM. EDUC.,44, 294 (1067).
1 Construction of the applicator; A, of pipets tor cutting; 8. dignment of pipet. for opplicotor; C, finished applicator; D, combustion boot containing liquid; E, applicator in operation.
Volume 48, Number 6, June 1971
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