Procedure for content uniformity— Perform the Assay on individual containers using Assay preparation 1 or Assay preparation 2, or both, as appropriate.

(Official January 1, 2007)

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

Assay preparation 1 (where it is represented as being in a single-dose container)—Constitute Oxacillin for Injection in a volume of water, accurately measured, corresponding to the volume of solvent specified in the labeling. Withdraw all of the withdrawable contents using a suitable hypodermic needle and syringe, and dilute quantitatively, and stepwise if necessary, with water to obtain a solution containing about 0.1 mg per mL of oxacillin. [NOTE—Use this solution on the day prepared.]

Assay preparation 2 (where the label states the quantity of oxacillin in a given volume of constituted solution)—Constitute Oxacillin for Injection with a volume of water, accurately measured, corresponding to the volume of solvent specified in the labeling. Dilute an accurately measured volume of the constituted solution quantitatively, and stepwise if necessary, with water to obtain a solution containing about 0.1 mg per mL of oxacillin (C19H19N3O5S). [NOTE—Use this solution on the day prepared.]

Procedure— Proceed as directed in the Assay under Oxacillin Sodium. Calculate the quantity, in mg, of oxacillin (C19H19N3O5S) in the constituted solution taken by the formula: in which L is the labeled quantity, in mg, of oxacillin in the container or in the volume of constituted solution taken; D is the concentration, in mg per mL, of oxacillin in Assay preparation 1 or in Assay preparation 2, on the basis of the labeled quantity in the container or in the volume of constituted solution taken, respectively; C is the concentration, in mg per mL, of USP Oxacillin Sodium RS in the Standard preparation; E is the oxacillin equivalent, in µg per mg, of USP Oxacillin Sodium RS; and rU and rS are the oxacillin peak responses obtained from the Assay preparation and the Standard preparation, respectively. Where the test for Uniformity of dosage units has been performed using the Procedure for content uniformity, use the average of these determinations as the Assay value.