Test solution— Use the Assay preparation, except to omit addition of the Internal standard solution.

(Official January 1, 2007)

Mobile phase— Mix 55 mL of a solution of water in methanol (5 in 100) with 1.0 mL of glacial acetic acid, dilute with water-washed 1,2-dichloroethane to 1000 mL, and mix. Degas before using. Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard solution— Dissolve 200 mg of acetaminophen in 4 mL of methanol, dilute with water-washed 1,2-dichloroethane to 200 mL, and mix. Keep the solution tightly stoppered and protected from light.

Standard preparation— Accurately weigh about 8 mg of USP Hydrocortisone RS, add 4 mL of methanol and 4.0 mL of Internal standard solution, dilute with chloroform to 100.0 mL, and mix to obtain a solution having a known concentration of about 0.08 mg of USP Hydrocortisone RS per mL.

Assay preparation— Transfer an accurately weighed quantity of Rectal Suspension, equivalent to about 8 mg of hydrocortisone, to a separator. Extract with four 20-mL portions of chloroform, filtering each portion through chloroform-washed cotton into a 100-mL volumetric flask. Add 4 mL of methanol and 4.0 mL of Internal standard solution, dilute with chloroform to volume, and mix. Pass the extract through a 0.5-µm porosity polytef membrane filter, discarding the first 20 mL of the filtrate.

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 5-µm packing L3. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 1.3 for acetaminophen and 1.0 for hydrocortisone; the resolution, R, between the analyte and internal standard is not less than 2.5; the column efficiency determined from the analyte peak is not less than 5000 theoretical plates; and the relative standard deviation for replicate injections is not more than 1.0%.

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 responses for the major peaks. Calculate the quantity, in mg, of hydrocortisone (C21H30O5) in the portion of Rectal Suspension taken by the formula: in which C is the concentration, in mg per mL, of USP Hydrocortisone RS in the Standard preparation; and RU and RS are the peak response ratios obtained from the Assay preparation and the Standard preparation, respectively.