(Official January 1, 2007)

Mobile phase , Phosphate buffer, Standard preparation, and Chromatographic system—Prepare as directed in the Assay under Cefoxitin Sodium.

Assay preparation 1 (where it is represented as being in a single-dose container)—Constitute Cefoxitin 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 with water to obtain a solution having a concentration of about 0.3 mg of cefoxitin per mL. Use this solution within 5 hours.

Assay preparation 2 (where the label states the quantity of cefoxitin in a given volume of constituted solution)—Constitute Cefoxitin for Injection in 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 with water to obtain a solution containing about 0.3 mg of cefoxitin per mL. Use this solution within 5 hours.

Procedure— Proceed as directed in the Assay under Cefoxitin Sodium. Calculate the quantity, in mg, of cefoxitin (C16H17N3O7S2) in the portion of constituted solution taken by the formula: in which L is the labeled quantity, in mg, in the portion of constituted solution taken; D is the concentration, in mg per mL, of Assay preparation 1 or Assay preparation 2, based on the volume of constituted solution taken and the extent of dilution; and the other terms are as defined therein.