FOR SOLID PACKAGED IN SINGLE-UNIT CONTAINERS: meets the requirements.

(Official January 1, 2007)

Mobile phase, Standard preparation, Resolution solution, and Chromatographic system— Proceed as directed in the Assay under Cephradine.

Assay preparation— Constitute Cephradine for Oral Suspension as directed in the labeling. Dilute an accurately measured volume of the suspension so obtained, freshly mixed and free from air bubbles, quantitatively with Mobile phase to obtain a solution containing about 0.5 mg of cephradine per mL. Filter a portion of this mixture through a filter having a porosity of 0.5 µm or finer, discarding the first 5 mL of the filtrate. Use the filtrate as the Assay preparation.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of cephradine (sum of cephradine and cephalexin) in each mL of constituted Oral Suspension taken by the formula: in which C is the concentration, in mg per mL, of USP Cephradine RS in the Standard preparation; P is the designated potency, in µg per mg, of USP Cephradine RS; L is the labeled quantity, in mg of cephradine, in each mL of the constituted Oral Suspension; D is the concentration, in mg of cephradine per mL, of the Assay preparation, based on the labeled quantity of cephradine per mL of constituted Oral Suspension and the extent of dilution; and rU and rS are the sums of the cephradine and cephalexin peak responses obtained from the Assay preparation and the Standard preparation, respectively.