Apply separately 10 µL of the Test solution
and 10 µL of each Standard solution
to a suitable thin-layer chromatographic plate (see Chromatography 621
) coated with a 0.25-mm layer of chromatographic silica gel mixture. Position the plate in a chromatographic chamber, and develop the chromatograms in a solvent system consisting of a mixture of alcohol, chloroform, and 5 M ammonium hydroxide (70:20:10) 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 allow the solvent to evaporate with the aid of warm circulating air. Examine the plate under short-wavelength UV light. Compare the intensities of any secondary spots observed in the chromatogram of the Test solution
with those of the principal spots in the chromatograms of the Standard solutions:
no secondary spot is more intense than the principal spot obtained from Standard solution A
(0.5%), and the sum of the intensities of all secondary spots obtained from the Test solution
does not exceed 1.0%.