A: A dilution of the Injection in methanol containing 1 mg of diazoxide per mL responds to the Thin-layer Chromatographic Identification Test 201, a solution of USP Diazoxide RS in methanol containing 1 mg per mL being used as the Standard solution. Develop the chromatogram with a solvent system consisting of a mixture of ethyl acetate, methanol, and ammonium hydroxide (17:4:3).

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation, both relative to the internal standard, as obtained in the Assay.

(Official January 1, 2007)

Mobile phase, Internal standard solution, Standard preparation, and Chromatographic system— Prepare as directed in the Assay under Diazoxide.

Assay preparation— Transfer an accurately measured volume of Injection, equivalent to about 45 mg of diazoxide, to a 50-mL volumetric flask, dilute with methanol to volume, and mix. Transfer 5.0 mL of this solution to a 100-mL volumetric flask, add 2.0 mL of Internal standard solution, dilute with a mixture of water and methanol (4:1) to volume, and mix.

Procedure— Proceed as directed for Procedure in the Assay under Diazoxide. Calculate the quantity, in mg, of C8H7ClN2O2S in each mL of the Injection taken by the formula: in which C is the concentration, in µg per mL, of USP Diazoxide RS in the Standard preparation; V is the volume, in mL, of Injection taken; and RU and RS are the peak response ratios obtained from the Assay preparation and the Standard preparation, respectively.