A: Cut open 1 Capsule, and remove the contents: the Capsule contents respond to Identification test A under Dihydrotachysterol Oral Solution.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation obtained as directed in the Assay.

(Official January 1, 2007)

Mobile phase , Standard preparation, System suitability preparation, and Chromatographic system—Prepare as directed in the Assay under Dihydrotachysterol.

Assay preparation— Combine the contents of not less than 20 Capsules. Transfer an accurately weighed quantity of Capsule contents, equivalent to about 500 µg of dihydrotachysterol, to a 50-mL volumetric flask, dissolve in 25 mL of Mobile phase, and mix. Dilute with Mobile phase to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Dihydrotachysterol. Calculate the quantity, in µg, of C28H46O in the portion of Capsules taken by the formula: in which C is the concentration, in µg per mL, of USP Dihydrotachysterol RS in the Standard preparation, and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.