A: Infrared Absorption 197K.

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

pH 7.5 Phosphate buffer— Dissolve 6.8 g of monobasic potassium phosphate and 1.6 g of sodium hydroxide in 1 L of water. Adjust with phosphoric acid or 2 N sodium hydroxide to a pH of 7.5.

Medium— Proceed as directed for Procedure for Method B under Apparatus 1 and Apparatus 2, Delayed-Release Dosage Forms, observing the following exceptions. Perform Acid stage testing, using 500 mL of 0.1 N hydrochloric acid for 1 hour; and perform Buffer stage testing, using 500 mL of pH 7.5 Phosphate buffer for not less than 8 hours.

Apparatus 1: 100 rpm.

Times: 1, 4, 6, and 9 hours.

Mobile phase— Prepare a filtered and degassed mixture of water, methanol, and glacial acetic acid (72:28:1), containing 0.73 g of sodium 1-heptanesulfonate. Make adjustments if necessary (see System Suitability under Chromatography 621).

System suitability solution— Dissolve suitable quantities of phenol and USP Morphine Sulfate RS in Mobile phase to obtain a solution containing about 0.1 mg of each per mL.

Standard solution— Dissolve an accurately weighed quantity of USP Morphine Sulfate RS in pH 7.5 Phosphate buffer, and dilute quantitatively, and stepwise if necessary, with pH 7.5 Phosphate buffer to obtain a solution having a known concentration corresponding to that of the solution under test.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 284-nm detector and a 3.9-mm × 30.0-cm column that contains 10-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.8 for phenol and 1.0 for morphine sulfate; the resolution, R, between the phenol and morphine sulfate peaks is not less than 2.0; the tailing factor for the morphine sulfate peak is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25 µL) of the Standard solution and the filtered portion of the solution under test into the chromatograph, record the chromatograms, and measure the peak responses. Determine the amount of (C17H19NO3)2·H2SO4·5H2O dissolved from the measured peak responses.

Tolerances— The percentage of the labeled amount of (C17H19NO3)2·H2SO4·5H2O dissolved in 1 hour conforms to Acceptance Table 3. The percentages of the labeled amount of (C17H19NO3)2·H2SO4·5H2O dissolved at the other times specified conform to Acceptance Table 2.

Standard solution— Prepare as directed in the Assay for Standard preparation.

Diluting solution, Buffer solution, Mobile phase, Resolution solution, and Chromatographic system— Proceed as directed in the Assay.

Test solution— Use the Assay preparation.

Procedure— Separately inject equal volumes (about 30 µL) of the Diluting solution and the Test solution into the chromatograph, record the chromatograms, and measure the peak areas, disregarding the peaks corresponding to those obtained in the chromatogram of the Diluting solution. Calculate the percentage of each impurity in the portion of Capsules taken by the formula: in which F is the relative response factor equal to 0.25 for any peak with a relative retention time between 2.2 and 2.8 and equal to 1.0 for all other impurity peaks; ri is the peak response for each impurity obtained from the Test solution; and rM is the peak response for morphine sulfate obtained from the Test solution: not more than 1.0% of any individual impurity is found; and not more than 2.0% of total impurities is found.

Diluting solution— Use water, and adjust with phosphoric acid to a pH of 3.60.

Buffer solution— Dissolve 13.8 g of monobasic sodium phosphate in 1 L of water.

Mobile phase— Prepare a filtered and degassed mixture of water, Buffer solution, acetonitrile, and triethylamine (874.5:100:25:0.5). Make adjustments if necessary (see System Suitability under Chromatography 621).

Resolution solution— Dissolve an accurately weighed quantity of USP Morphine Sulfate RS in Diluting solution to obtain a solution having a known concentration of about 10 mg per mL. Transfer 1.0 mL of this solution to a 10-mL volumetric flask containing 2.0 mL of 30 percent hydrogen peroxide. Heat, with stirring, in a water bath at a temperature of about 80 for about 30 minutes. Cool to room temperature, dilute with Diluting solution to volume, and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Morphine Sulfate RS in Diluting solution to obtain a solution having a known concentration of about 1.0 mg per mL.

Assay preparation— Accurately weigh and transfer the contents of 10 Capsules to a suitable volumetric flask to obtain a solution having a final concentration of about 1 mg of morphine sulfate per mL. Add an amount of methanol equivalent to 4.5% of the flask volume. Mix for about 30 minutes, gently swirling every 5 minutes. Add Diluting solution up to about half of the flask volume, and sonicate for 5 minutes to dissolve. Rinse the inner wall and neck of the flask with an amount of methanol equivalent to about 0.5% of the flask volume, dilute with Diluting solution to volume, and mix. Pass through a suitable filter, and use the clear filtrate.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 245-nm detector, a suitable guard column that contains packing L1, and a 3.9-mm × 30.0-cm column that contains 10-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are between 1.2 and 1.4 for morphine N-oxide and between 2.2 and 2.8 for pseudomorphine; and the resolution, R, between the morphine N-oxide and morphine sulfate peaks is not less than 2.0. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 30 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the quantity, in mg, of morphine sulfate pentahydrate [(C17H19NO3)2·H2SO4·5H2O] in the portion of Capsules taken by the formula: in which C is the concentration, in mg per mL, of USP Morphine Sulfate RS in the Standard preparation; V is the volume of the volumetric flask used to prepare the Assay preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.