Medium: water; 900 mL.

Apparatus 1: 100 rpm.

Time: 30 minutes.

Procedure— Determine the amount of dicloxacillin (C19H17Cl2N3O5S) 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 Dicloxacillin Sodium RS in the same Medium.

Tolerances— Not less than 75% (Q) of the labeled amount of C19H17Cl2N3O5S is dissolved in 30 minutes.

Diluent, Mobile phase, Standard preparation, and Chromatographic system— Proceed as directed in the Assay under Dicloxacillin Sodium.

Assay preparation— Remove, as completely as possible, the contents of not fewer than 10 Capsules, and weigh. Mix, and transfer an accurately weighed portion of the powder, equivalent to about 200 mg of dicloxacillin (C19H17Cl2N3O5S), to a 200-mL volumetric flask, dilute with Diluent to volume, and mix for 10 minutes with the aid of a magnetic stirrer. Filter about 25 mL of the resulting solution, discarding the first 5 mL of the filtrate. Use the clear filtrate as the Assay preparation. [note—Use this Assay preparation promptly, or refrigerate and use on the day prepared.]

Procedure— Proceed as directed for Procedure in the Assay under Dicloxacillin Sodium. Calculate the quantity, in mg, of dicloxacillin (C19H17Cl2N3O5S) in the portion of Capsule contents taken by the formula: in which the terms are as defined therein.