A: Ash the contents of 1 Capsule, dissolve the residue in 10 mL of dilute hydrochloric acid (1 in 12), and filter: the filtrate responds to the tests for Calcium 191.

B: Empty the contents of 1 Capsule into a conical flask, add isopropyl alcohol to obtain a concentration of 10 mg of docusate calcium per mL, and mix. This solution responds to Identification test C under Docusate Calcium.

Medium: water; 500 mL.

Apparatus 2: 50 rpm.

Time: 15 minutes.

Procedure— Place 1 Capsule in each vessel, and allow the Capsule to sink to the bottom of the vessel before starting rotation of the blade. Observe the Capsules, and record the time taken for each capsule shell to rupture.

Tolerances— The requirements are met if all of the Capsules tested rupture in not more than 15 minutes. If 1 or 2 of the Capsules rupture in more than 15 but not more than 30 minutes, repeat the test on 12 additional Capsules. Not more than 2 of the total of 18 Capsules tested rupture in more than 15 but not more than 30 minutes.

SOLID-FILLED CAPSULES: meet the requirements for Content Uniformity.

SOLUTION-FILLED CAPSULES: meet the requirements for Weight Variation.

(Official January 1, 2007)

Basic fuchsin solution— Dissolve 100 mg of basic fuchsin, previously recrystallized from alcohol, in 3 mL of methanol in a 100-mL volumetric flask, dilute with water to volume, and mix. Filter prior to use.

Standard preparation— Weigh accurately about 50 mg of USP Docusate Calcium RS into a 10-mL volumetric flask, dissolve in isopropyl alcohol, dilute with isopropyl alcohol to volume, and mix. Transfer 5.0 mL of this solution to a 500-mL volumetric flask containing 90 mL of a mixture of water and isopropyl alcohol (1:1) with swirling, dilute with water to volume, and mix. The concentration of USP Docusate Calcium RS in the Standard preparation is about 50 µg per mL.

Assay preparation— To 10 Capsules in a 400-mL beaker add 300 mL of hot water. Heat on a steam bath, with occasional stirring, until the Capsules are completely disintegrated, cool, and transfer with the aid of 100 mL of warm water to a 1000-mL volumetric flask. Rinse the beaker with 100 mL of isopropyl alcohol, add the rinsing to the volumetric flask, and shake to dissolve any previously undissolved particles. Dilute with a mixture of water and isopropyl alcohol (1:1) to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with water to volume, and mix.

Procedure— Transfer 4.0 mL of the Standard preparation to a 125-mL separator. To a second 125-mL separator transfer an accurately measured volume of the Assay preparation, equivalent to 200 to 240 µg of docusate calcium, and add a solution of isopropyl alcohol (1 in 100), if necessary, to bring the volume of the solution in the separator to 4.0 mL. To each separator transfer 20.0 mL of pH 1.2 hydrochloric acid buffer (see under Solutions in the section Reagents, Indicators, and Solutions) and 2.0 mL of Basic fuchsin solution, add 20 mL of chloroform to each, and shake for 1 minute. Allow the phases to separate, and transfer the chloroform extracts, through separate pledgets of absorbent cotton, into separate 100-mL volumetric flasks. Extract each of the solutions in the separators in the same manner with additional 20-mL portions of chloroform until no more color is visible in the extract, and pass each extract through the pledget of cotton used for the preceding extract into the flask containing the preceding extract. Dilute the contents of each flask to volume by passing chloroform through the cotton pledgets that had been used to filter the extracts, and mix. Concomitantly determine the absorbances of the solutions in 1-cm cells at the wavelength of maximum absorbance at about 545 nm, with a suitable spectrophotometer, using chloroform as the blank. Calculate the quantity, in mg, of C40H74CaO14S2 in each Capsule taken by the formula: in which C is the concentration, in µg per mL, of anhydrous docusate calcium in the Standard preparation; V is the volume, in mL, of Assay preparation taken; and AU and AS are the absorbances of the solutions from the Assay preparation and the Standard preparation, respectively.