A: The chromatogram of the Assay preparation obtained as directed in the Assay exhibits a major peak for ceftizoxime, the retention time of which corresponds to that exhibited in the chromatogram of the Standard preparation obtained as directed in the Assay.

B: It responds to the tests for Sodium 191.

pH 3.6 Buffer— Dissolve 1.42 g of citric acid monohydrate and 1.73 g of dibasic sodium phosphate in water to obtain 1000 mL of solution.

pH 7.0 Buffer— Dissolve 3.63 g of monobasic potassium phosphate and 10.73 g of dibasic sodium phosphate in water to obtain 1000 mL of solution.

Mobile phase— Prepare a mixture of pH 3.6 Buffer and acetonitrile (about 9:1). Filter through a filter (1 µm or finer porosity), and degas. Adjust the composition, if necessary, to meet the performance requirements under Chromatographic system.

Internal standard solution— Dissolve 1.2 g of salicylic acid in 10 mL of methanol, and dilute with pH 7.0 Buffer to obtain 200 mL of solution.

Standard preparation— Dissolve a suitable quantity of USP Ceftizoxime RS, accurately weighed, in pH 7.0 Buffer to obtain a solution having a known concentration of about 1 mg of ceftizoxime (C13H13N5O5S2) per mL. Transfer 2.0 mL of this solution to a 100-mL volumetric flask, add 5.0 mL of Internal standard solution, dilute with pH 7.0 Buffer to volume, and mix. This Standard preparation contains about 0.02 mg of ceftizoxime per mL.

Assay preparation— Using a suitable quantity of Ceftizoxime Sodium, accurately weighed, proceed as directed under Standard preparation.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 4.0-mm × 30-cm column that contains 5- to 10-µm packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed under Procedure: the column efficiency determined from the analyte peak is not less than 2000 theoretical plates; the tailing factor for the analyte peak is not more than 2, the resolution; R, between the analyte and internal standard peaks is not less than 4; and the relative standard deviation for replicate injections is not more than 2%.

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. The relative retention times are about 0.6 for ceftizoxime and 1.0 for salicylic acid. Calculate the quantity, in µg, of ceftizoxime per mg of the Ceftizoxime Sodium taken by the formula: in which C is the concentration, in mg of ceftizoxime (C13H13N5O5S2) per mL, of the Standard preparation; M is the concentration, in mg per mL, of the Assay preparation based on the weight of Ceftizoxime Sodium taken and the extent of dilution; and RU and RS are the peak response ratios of the ceftizoxime peak to the internal standard peak obtained from the Assay preparation and the Standard preparation, respectively.