A Spray Technique for the Preparation of Thin-Layer Chromatography Plates We have found a spray technique for the preparation of thin-layer chromatography plates to be at least equal with the traditional spreading technique. Typically, the spray technique employs some type of device for spraying a fine mist of absorbent onto a supporting plate.1.z.3 We used a commercial sprayer (Sears, Roebuck and Company) which included a compressor rated at 35 p.s.i. and a spray gun. The gun emitted the spray in a band instead of the circular pattern found in most aerosols. The band spray could be adjusted to either the horizontal or the vertical. Through trial and error, we found that the best results could be obtained from a band of spray in the horizontal position. Also used were Silica Gel absorbent and 20 x 20 cm glass supportingplates. The actual spray technique was quite simple. Ten glass plates were first thoroughly cleaned with a strong detergent, rinsed with deionized water, and dried completely. They were placed on a level surface in two rows of five plates, all closely spaced together (% cm apart). A slurry was mixed in the container of the spray gun using 1g of Silica Gel and 1.8 ml of water, or 10 g of Silica Gel and 18 ml of water per plate. The slurry was thoroughly mixed by swirling the contents of the container after which it was attached to the gun and spraying was begun. The plates were sprayed while holding the gun at a 45" an& about 18 in. above the dates. The band of mist was nsrallel to the rows of d a t e s and was snraved . . evenlv and ranidlv over the entire surface of the d a t e confirmration. This orocedure can be easilv develooed with a minimum of orac-
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lowed to cool, and stored for later use. To check the consistency of our sprayed plates we chose 5 plates at random from within a batch and from batch to batch and ran them with a mixture of 5 compounds, with the same 5 compounds spotted in 12 columns across the plates. All plates were chromatographed in the same manner. The table shows the average Rr values and standard deviations of 5 sprayed plates within a batch and from batch to batch. Average R, Values and Standard Deviations of Sprayed Plates* Compound Caffeine Nicotine Quinine Brucine Strychnine
Rr Valuesb 0.674 0.891 0.270 0.401 0.564
f 0.014" f 0.013 f 0.016 f 0.010 f 0.010
*Absorbent was Silica AR T L C T G F ; solvent system was benzene-ethyl acetate-diethylamine (10: 10: 3); visualizer was uv; solvent front moved a distance of 15 cm. * Soraved d a t e s were selected a t random from varioua * prepmeo oatcher a s wel. a s from the .wme batch. * E a c h H! value reporrcd is a n average taken from 5 dif. ferent plarcs a n d t h e standard dewation is for n = 60.
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It is worth noting here that the plates being chromatographed were ''scored" to prevent zone migration of compounds on the plate. Scoring simply means, in effect, the division of a plate into smaller plates by breaking the absorbent coating at constant intervals. We found that our sprayed plates were of a quality suitable far research as well as for the student laboratory. 'Reirsema, James M., "Thin-Layer Chromatography," Reinhold Publishing Corp., New York, 1963,p. 40. Bekersky, I., Anal. Chem., 35,261 (1963). Morita, K. and Haruta, F., J. Chromatogr., 12,412 (1963). 4Stock, R. and Rice, C. B. F., "Chromatographic Methods," 2nd Ed., Chapman and Hall Ltd., London, 1967, p. 171.
Anpelo Stale IIniversily San Anwlo, Texas 7fi901
Paul D. Swaim Vincent M. Loyola H. D. Harlan Michael J. Carlo
Volume 51, Number 5, May 1974
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