A: Infrared Absorption 197M.

B: The chromatogram of the Assay preparation obtained as directed in the Assay exhibits a major peak for glyburide, the retention time of which corresponds to that exhibited in the chromatogram of the Standard preparation, both relative to the internal standard, as obtained in the Assay.

Mobile phase— Prepare as directed in the Assay.

Test solution— To about 10 mg of Glyburide, accurately weighed, add 10 mL of acetonitrile, and shake to dissolve. Add 4 mL of water, and mix.

Chromatographic system— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L7. The flow rate is about 2 mL per minute. Chromatograph the Test solution, and record the peak responses as directed for Procedure: the column efficiency is not less than 3500 theoretical plates.

Procedure— Inject a volume (about 20 µL) of the Test solution into the chromatograph, record the chromatogram, and measure the areas for the major peaks. Calculate the percentage of each impurity in the portion of Glyburide taken by the formula: in which ri is the peak response for each impurity; and rs is the sum of the responses of all of the peaks: not more than 1.5% of any impurity, which elutes before glyburide, is found; not more than 0.5% of any other individual impurity is found; and not more than 2.0% of total impurities is found.

Mobile phase— Dissolve 2.6 g of monobasic ammonium phosphate in 450 mL of water. Add 550 mL of acetonitrile, filter, and degas. Adjust, if necessary, with phosphoric acid or sodium hydroxide to a pH of 5.25 ± 0.30. Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard solution— Dissolve progesterone in acetonitrile to obtain a solution containing about 0.2 mg per mL.

Standard preparation— To about 10 mg of USP Glyburide RS, accurately weighed, add 20.0 mL of Internal standard solution, and shake vigorously to dissolve. Add 4.0 mL of water, and mix.

Assay preparation— To about 10 mg of Glyburide, accurately weighed, add 20.0 mL of Internal standard solution, and shake vigorously to dissolve. Add 4.0 mL of water, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L7. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.4 for glyburide and 1.0 for progesterone; the resolution, R, between glyburide and progesterone is not less than 5.0; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the heights for the major peaks. Calculate the quantity, in mg, of C23H28ClN3O5S in the portion of Glyburide taken by the formula: in which WS is the weight, in mg, of USP Glyburide RS taken to prepare the Standard preparation; and RU and RS are the peak height ratios obtained from the Assay preparation and the Standard preparation, respectively.