(Official January 1, 2007)

Mobile phase— Dissolve 5.5 g of sodium 1-heptanesulfonate in 700 mL of water. Add 300 mL of methanol and 10 mL of glacial acetic acid, mix, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Morphine Sulfate RS in Mobile phase, and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.5 mg per mL. [NOTE—Prepare this solution fresh daily.]

System suitability preparation— Prepare a solution in Mobile phase containing, in each mL, about 0.24 mg of USP Morphine Sulfate RS and 0.15 mg of phenol.

Assay preparation— Transfer 1 Suppository to a 60-mL separator containing 20 mL of chloroform and 20 mL of 0.01 N hydrochloric acid, and shake to dissolve the Suppository. Transfer the chloroform layer to a 250-mL separator. Extract the aqueous layer with a second 20-mL portion of chloroform, and combine the chloroform extracts in the 250-mL separator. Wash the chloroform extracts with two additional 20-mL portions of 0.01 N hydrochloric acid, combine the aqueous layers in a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix. Pass this solution through a filter having a 0.45-µm or finer porosity, discarding the first 4 mL of the filtrate.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 284-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The column temperature is maintained at 30. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation and the System suitability preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.7 for phenol and 1.0 for morphine; the resolution, R, between phenol and morphine is not less than 2.0; the tailing factor for the morphine peak is not more than 2.0; and the relative standard deviation for replicate injections of the Standard preparation is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 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 morphine sulfate pentahydrate [(C17H19NO3)2·H2SO4·5H2O] in the Suppository taken by the formula: in which 758.83 and 668.77 are the molecular weights of morphine sulfate pentahydrate and anhydrous morphine sulfate, respectively; C is the concentration, in mg per mL, of anhydrous morphine sulfate in the Standard preparation, as determined from the concentration of USP Morphine Sulfate RS corrected for moisture content by a titrimetric water determination; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.

Morphine Sulfate	50 mg
Silica Gel	25 mg
Polyethylene Glycol Base, a sufficient quantity to make one suppository

Mobile phase, Standard preparation, System suitability preparation, and Chromatographic system— Proceed as directed in the Compliance assay for suppositories compounded in fatty acid base.

Assay preparation— Transfer 1 Suppository to a 100-mL volumetric flask, and add about 70 mL of Mobile phase. Sonicate for 15 minutes to dissolve the Suppository, cool, dilute with Mobile phase to volume, and mix. Pass a 10-mL portion of the solution through a filter having a 0.45-µm or finer porosity, discarding the first 4 mL of the filtrate.

Procedure— Proceed as directed in the Compliance assay for suppositories compounded in fatty acid base. Calculate the quantity, in mg, of morphine sulfate pentahydrate [(C17H19NO3)2·H2SO4·5H2O] in the Suppository taken by the formula: in which the terms are as defined therein.