Medium: water;900mL.

Apparatus 1: 100rpm.

Time: 45minutes.

Procedure— Determine the amount of oxacillin (C19H19N3O5S)by a suitable validated spectrophotometric analysis of a filtered portion of the solution under test,suitably diluted with Dissolution Medium,if necessary,in comparison with a Standard solution having a known concentration of USP Oxacillin Sodium RSin the same medium.

Tolerances— Not less than 75%(Q)of the labeled amount of C19H19N3O5Sis dissolved in 45minutes.

Mobile phase ,Standard preparation,and Chromatographic system—Proceed as directed in the Assayunder Oxacillin Sodium.

Assay preparation— Remove,as completely as possible,the contents of not less than 10Capsules,and weigh.Mix,and transfer an accurately weighed portion of the powder,equivalent to about 100mg of oxacillin (C19H19N3O5S),to a 200-mLvolumetric flask,add water to volume,and mix for 10minutes with the aid of a magnetic stirrer.Filter about 25mLof the resulting solution,discarding the first 5mLof the filtrate.Transfer 10.0mLof the clear filtrate to a 50-mLvolumetric flask,dilute with water to volume,and mix.[NOTE—Use this Assay preparation on the day prepared.]

Procedure— Proceed as directed for Procedurein the Assayunder Oxacillin Sodium.Calculate the quantity,in mg,of oxacillin (C19H19N3O5S)in the portion of Capsule contents taken by the formula: in which the terms are as defined therein.