A: It conforms to the description for Ground Digitalis in the section Botanic characteristics under Digitalis.

B: Transfer 100 mg to a 15-mL centrifuge tube containing 2.0 mL of diluted alcohol and 1.0 mL of lead acetate TS, mix, shake, and boil for 2 minutes. Centrifuge, decant the supernatant into a second 15-mL centrifuge tube, add 2.0 mL of chloroform, and mix. Centrifuge, then remove the lower layer, and filter it through a chloroform-washed small column of anhydrous sodium sulfate (100 to 300 mg) into a 5-mL centrifuge tube. Evaporate the chloroform solution under a stream of nitrogen to dryness, and dissolve the residue in 100 µL of a mixture of methanol and chloroform (1:1). Prepare a Standard solution in the same manner, using 100 mg of USP Digitalis RS (Standard solution A). Prepare a second Standard solution by dissolving USP Digitoxin RS and USP Gitoxin RS in a mixture of methanol and chloroform (1:1) such that the final concentration of each is approximately 0.2 mg per mL (Standard solution B). Apply 10 µL of the test solution, 10 µL of Standard solution A, and 10 µL of Standard solution B, each as a narrow band about 15 mm long, to a suitable thin-layer chromatographic plate (see Chromatography 621) coated with a 0.25-mm layer of chromatographic silica gel mixture, and allow the bands to dry. Develop the chromatogram in a saturated chamber, using a solvent system consisting of a mixture of ethyl acetate, methanol, and water (30:4:3) until the solvent front has moved about 15 cm from the origin. Mix 10 mL of chloramine T solution (3 in 100) with 40 mL of a 1 in 4 solution of trichloroacetic acid in alcohol (store the mixture in a cool place, and use it within 1 week), and spray the air-dried chromatographic plate with this mixture. Heat the plate at 110 for 15 to 20 minutes, and examine it under long-wavelength UV light. Locate the 2 prominent bands obtained from Standard solution A corresponding in RF value to the 2 bands obtained from Standard solution B. The chromatogram obtained from the solution under test shows bands corresponding to them, and also shows bands corresponding to the 3 other bands most prominent in the chromatogram from Standard solution A but of lower RF value. Relative RF values for the 5 bands are: 1.0 (digitoxin); 0.8 to 0.9 (gitoxin); 0.6 to 0.7; 0.4 to 0.5; and 0.3 to 0.4.

(Official January 1, 2007)