Medium: 0.05 M pH 6.8 potassium phosphate buffer; 900 mL.

Apparatus 1: 100 rpm.

Time: 30 minutes.

Procedure— Determine the amount of cloxacillin (C19H18ClN3O5S) dissolved by employing the method set forth in the Assay, in comparison with a Standard solution having a known concentration of USP Cloxacillin Sodium RS in the Dissolution Medium.

Tolerances— Not less than 80% (Q) of the labeled amount of cloxacillin (C19H18ClN3O5S) is dissolved in 30 minutes.

(Official January 1, 2007)

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

Assay preparation— Weigh and finely powder the contents of not fewer than 10 Capsules. Transfer an accurately weighed quantity of the powder, equivalent to about 100 mg of cloxacillin, to a 200-mL volumetric flask, dilute with Buffer to volume, mix, and stir for 10 minutes. Filter about 25 mL of this mixture, discarding the first 5 mL of the filtrate. Use the clear filtrate as the Assay preparation.

Procedure— Proceed as directed for Procedure in the Assay under Cloxacillin Sodium. Calculate the quantity, in mg, of cloxacillin (C19H18ClN3O5S) in the portion of Capsule contents taken by the formula: in which the terms are as defined therein.