Procedure
Apply separate 5-µL portions of the
Test solution and the
Standard solutions to the starting line of a suitable thin-layer chromatographic plate (see
Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture, previously washed with methanol until the solvent front reaches the top of the plate, dried first in air and then at 100
for 20 minutes, and cooled in a desiccator. Allow the spots to dry. Line a suitable chromatographic chamber with filter paper, saturate the paper with 100 mL of a solvent system consisting of a mixture of ethyl acetate, glacial acetic acid, and water (15:5:5), and allow to stand for about 30 minutes. Place the plate in the chamber, and develop the chromatogram until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chamber and dry at 100
for 15 minutes. Spray the plate uniformly with a detection reagent consisting of a freshly prepared mixture of equal volumes of potassium ferricyanide solution (1 in 100) and ferric chloride solution (1 in 5). Dry the plate in a current of warm air for about 5 minutes or until a spot from
Standard solution B is visible. Examine the chromatograms in ordinary light: the
RF value of the principal spot from the
Test solution corresponds to that obtained from
Standard solution A. No spot other than the principal spot obtained from the
Test solution exceeds in size or intensity the principal spot obtained from
Standard solution B (0.4%, corresponding to 0.2% of related compounds, the response factors for which are about double that of oxprenolol hydrochloride).