Medium: water;500mL.

Apparatus 2: 50rpm.

Time: 15minutes.

Procedure— Place 1Capsule 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 15minutes.If 1or 2of the Capsules rupture in more than 15but not more than 30minutes,repeat the test on 12additional Capsules.Not more than 2of the total of 18Capsules tested rupture in more than 15but not more than 30minutes.

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

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

Methanol–water solution— Transfer 180mLof water to a 1000-mLvolumetric flask,dilute with methanol to volume,and mix.

Tetrabutylammonium hydroxide–methanol solution— Prepare a solution of tetrabutylammonium hydroxide in methanol containing 25g per 100mL.

Mobile phase— Mix 180mLof water,6.0mLof glacial acetic acid,and 8.0mLof Tetrabutylammonium hydroxide–methanol solutionin a 1000-mLvolumetric flask,dilute with methanol to volume,and mix.The water concentration may be varied to meet system suitability requirements and to provide a suitable elution time (about 5minutes)for docusate potassium.

Standard preparation— Dissolve in Methanol–water solutiona suitable quantity,accurately weighed,of USP Docusate Sodium RS,and dilute quantitatively with the same solvent to obtain a solution having a known concentration of about 4mg per mL,calculated on the anhydrous basis.

Assay preparation for solid-filled capsules— Open and empty into a suitable container the contents of a counted number of Capsules,equivalent to about 1000mg of docusate potassium.Place the capsule shells in the container,and add 250.0mLof Methanol-water solution.Shake by mechanical means for 20minutes,and clarify a portion of the mixture by centrifuging.Pass a portion of the clear supernatant through a membrane filter having a 0.5-µm or finer porosity.

Assay preparation for solution-filled capsules— Cut open a counted number of Capsules,equivalent to about 2.5g of docusate potassium,and place the shells and contents in a suitable container.Add about 25mLof methanol,agitate for not less than 2minutes,and decant the liquid into a 200-mLvolumetric flask.Repeat the addition of methanol,agitation,and decanting not less than four times.Dilute with methanol to volume,and mix.Pipet 8mLof this solution into a 25-mLvolumetric flask,add 4.5mLof water,dilute with methanol to volume,and mix.

Chromatographic system (see Chromatography á621ñ)—The chromatograph is equipped with a refractive index detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.8mLper minute.Chromatograph five replicate injections of the Standard preparation,and record the peak responses as directed for Procedure:the relative standard deviation is not more than 3.0%.

Procedure— Separately inject equal volumes (about 100µL)of the Standard preparationand the appropriate Assay preparationinto the chromatograph by means of a suitable microsyringe or sampling valve,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of docusate potassium (C20H37KO7S)in each solid-filled Capsule taken by the formula: and calculate the quantity,in mg,of docusate potassium (C20H37KO7S)in each solution-filled Capsule taken by the formula: in which 460.67and 444.56are the molecular weights of docusate potassium and docusate sodium,respectively;Cis the concentration,in mg per mL,of anhydrous USP Docusate Sodium RSin the Standard preparation;Nis the number of Capsules taken;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.