In the Laboratory edited by
Cost-Effective Teacher
Harold H. Harris University of Missouri—St. Louis St. Louis, MO 63121
A Preparative TLC Applicator Tom Lyons Fisher* and Charles P. Gilman Department of Chemistry, Juniata College, Huntingdon, PA, 16652-2119; *
[email protected] A mechanical applicator is essential for successful preparative thin-layer chromatography (PTLC). A number of PTLC applicator designs have appeared in this Journal, but only one has proven itself worthy of commercialization (1, 2). However, at ~$200 apiece, it is probably too expensive for use in most student laboratories where multiple units would be required. The device described here retains the capability of the commercial applicator but is more easily and inexpensively constructed from readily available materials. The slider (Fig. 1) is a 14-in. piece of 1 × 1 × 1⁄8-in. Lshaped aluminum material. Two holes 23⁄4 in. apart were drilled in the slider and countersunk to accommodate 1⁄4 × 21⁄2-in. flat-head machine screws. Each screw was locked into place with a washer, a lock washer, and a nut. The handles were removed from two standard-taper size 13 PTFE stoppers (from broken volumetric flasks) and the stoppers were joined by a 2-in. section of Tygon tubing‚ 1⁄2-in. i.d., in which a hole was drilled (using a cork borer) to grip a 1⁄2dram glass vial. Two 3⁄8 × 3⁄4 × 0.030-in. compression springs, a stopper, and a wing nut were placed on each screw. This arrangement permits precise height adjustment. A capillary tube was bent into an L shape and a tip was drawn at one end before placing the other end in the vial. To use the applicator, a preparative TLC plate is placed on a book near the edge of the lab bench. The slider is held to the edge of the bench and the height of the capillary is
Figure 1. View of the central portion of the applicator.
adjusted using the wing nuts so that its tip just touches the plate. After some sample is placed in the vial, the applicator is slid back and forth along the edge of the bench at a speed that allows delivery of the appropriate amount of sample on each pass. Literature Cited 1. Altman, L. J.; Trudell, J. R. J. Chem. Educ. 1970, 47, 404. 2. Kimble Kontes Chromatography Products Catalog; Kimble Kontes: Vineland, NJ, 2000; p 117.
JChemEd.chem.wisc.edu • Vol. 78 No. 3 March 2001 • Journal of Chemical Education
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