ANALYTICAL CHEMISTRY
2038 The amount of ultraviolet-absorbing steroid detectable by the visual and photographic methods is about 5 y per square cm. of filter paper. Photography of Chromogenic Compounds. The use of the visible-light modification of the scanner-camera derives its greatest utility in the preparation of permanent photographic records of developed paper chromatograms. This is especially true if the color developed on the paper fades rapidly after development. Contact paper is used as in the ultraviolct 1 2 3 4
Tray for Dipping Chromatograms Nelle J. Morris and Austin C. F. Mason, Southern Regional Research Branch, Agricultural Research Service, U. S. Deportment of Agriculture, New Orleons, Lo.
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chromatograms, after development, generally require
P the application of reagents for locating the positions of the separated components. Depending on the reagent, the solvent in which the reagent is dissolved may be allowed to evaporate and the dried chromatogram heated or allowed to stand a t room temperature until reactions have produced colored spots on the paper. The reagents are usually sprayed on the chromatogram. However, it is often better to dip the chromatograms in solutions of the reagents in organic solvents (I-S'), in which the separated components are not readily soluble. ilmong the advantages of dipping are uniform application of the reagent to the chromatogram and the avoidance of mists. In order to dip the chromatograms conveniently, an apparatus is needed that will achieve positive and uniform wetting of either large or small papers, will not exert much drag on the paper (danger of tearing u et paper), will require only a small volume of solvent, and will be easy to clean, inert to corrosive reagents, and free from sources of contamination-e. g., metals.
1 9 3 4
Figure 2. Comparison of photographs of same papergram Papergram developed on Whatman Yo. 1 paper in toluene-propylene glycol (6).
UV. Ultraviolet photography T C . Vkible-light photography tetrazolium color development
after
Channels, top t o bottom: 1, 4. 11-Epihydrocortisone, hydrocortisone, cortisone, ll-desoryhydrocortisone 2 . Tetrahydrocortisone (TC), tetrahydro-1 1-desoxyhydrocortisone (TC), tetrahydro 11 -dehydrocorticosterone (TC) 3. Tetrahydrohydrocortisone (TC), pregnenetriolone (UV), 21-desoxyhydrocortisone (UV)
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photography; however, a somewhat longer exposure is necessary in this case. I n the use of this device to photograph chromatograms with developed tetrazolium color ( 3 ) ,a pretreatment of the processed paper is desirable, This pretreatment consists of: (1) washing excess tetrazolium reagent and alkali from the paper with water (deionized water is used in this laboratory), and ( 2 ) moistening the washed paper with 50% (by volume) aqueous propyIene glycol. The irashing and moistening operations are performed while the chromatogram is supported on a sheet of stainless steel a t an angle of 45" in a sink. The use of propylene glycol enhances the transparency of the paper. Figure 2 s h o w photographs of the same paper chromatogram, first, by ultraviolet photography and, second, by visible-light photography after tetrazolium color has been developed on the paper. LITERATURE CITED
Haines, W. J., "Recent Progress in Hormone Research," vol. 7, pp. 255-305,Academic Press, New York, 1952. Haines, W. J., Drake, K . d..Federatwn Proc. 9,180-1 (1950). Knauff, R.E.,Xielson, E. D., Haines, W. J., J . A m . Chem. SOC. 75, 4868-9 (1953).
Markham, R., Smith, J. D., Biochem. J . 45, 294-8 (1949). Zaffaroni, A.,Burton, R. B., Keutmann, E. H., Science 111, 6-8 (1950).
A tray that meets these requirements and provides a convenient means for dipping large chromatograms is made from a longitudinally split section of borosilicate glass tubing. For a roller to hold the paper beneath the surface of the reagent solution, a glass tube of smaller diameter, sealed a t the ends, is fitted into fixed glass sleeves in such a manner that the tube rotates freely. A 24.5 X 2.75 inch tray d l accommodate chromatograms up to 22.5 inches in width. The exact dimensions of the tray (or roller) are not important; however, trays much smaller in diameter would not be convenient for use with large papers. The glass sleeves were prepared from glass tubing having an inside diameter slightly larger than the short pieces of glass rod that seal the ends of the roller and fit into the sleeves. The sleeves were slipped on the roller and then sealed permanently t o the tray. In use, a dried paper chromatogram is slipped under the roller tube and drawn quickly through the reagent solution (approximately 50 ml.). This device is probably suitable for other laboratory coating and impregnating processes. LITERATURE CITED
(1) Jepson, J. B., Smith, I., Nature 172, 1101 (1953). (2) Smith, Ivor, Ibid., 171, 43 (1953). (3) Trevelyan, W. E.,Proctor, D. P., Harrison, J. S., Ibid., 166,
444 (1950).
