Packaging and storage—
Preserve in collapsible tubes or tight containers. Store at 25
, excursions permitted between 15
and 30
. Protect from freezing.
Thin-layer chromatographic identification test 
201
—
Test solution—
Transfer about 1.5 g of Ointment to a glass-stoppered, 50-mL centrifuge tube. Add 15 mL of methanol–hydrochloric acid solution prepared by mixing 1 volume of dilute hydrochloric acid (1 in 120) with 4 volumes of methanol. Shake to obtain a homogeneous mixture. Add 30 mL of solvent hexane, mix for 10 minutes, and centrifuge. Using a suitable syringe, transfer the lower aqueous phase to a second centrifuge tube, add about 20 mL of water, and mix. Extract this aqueous mixture with chloroform by shaking, centrifuging, and removing the lower, chloroform phase with a syringe. Evaporate the chloroform on a steam bath with the aid of a stream of nitrogen to dryness, cool, and dissolve the residue in chloroform to obtain a solution containing about 150 µg of betamethasone dipropionate per mL.
Application volume:
40 µL.
Developing solvent system:
a mixture of chloroform and acetone (7:1).
Procedure—
Proceed as directed in the chapter.
Assay—
Internal standard solution and Standard preparation—
Prepare as directed in the
Assay under
Betamethasone Dipropionate Cream, except to use alcohol containing acetic acid (1 in 1000) as the solvent.
Assay preparation—
Transfer an accurately weighed quantity of Ointment, equivalent to about 2 mg of betamethasone dipropionate, to a capped 50-mL centrifuge tube. Add 5.0 mL of
Internal standard solution and 10.0 mL of alcohol containing acetic acid (1 in 1000). Heat in a water bath at 70
, shaking intermittently until the assay specimen melts. Remove from the bath, and shake vigorously until the ointment has solidified. Repeat the heating and shaking operation. Proceed as directed for
Assay preparation in the
Assay under
Betamethasone Dipropionate Cream, beginning with “Freeze in an ice-methanol bath.”
