Procedure
Apply separately 20 µL of the
Test preparation and 20 µL of the
Standard preparation to a suitable thin-layer chromatographic plate (see
Chromatography
621![](images/chars/rang.gif)
) coated with a 0.25-mm layer of chromatographic silica gel. Allow the spots to dry, place the plate in a chromatographic chamber, and develop the chromatograms in a solvent system consisting of a mixture of 1,4-dioxane, toluene, and 13.5
M ammonium hydroxide (60:40:1) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the developing chamber, mark the solvent front, and dry the plate in a current of air. Expose the plate to iodine vapors for 1 hour, and air-dry until the iodine has dissipated. Compare the intensities of any secondary spots observed in the chromatogram of the
Test preparation with that of the principal spot in the chromatogram of the
Standard preparation: no individual secondary spots in the chromatogram of the
Test preparation are larger or more intense than the principal spot produced by the
Standard preparation, corresponding to not more than 0.375%, and the total of all such secondary spots observed is not more than 2.0%.