0.2 M Monobasic ammonium phosphate, Mobile phase, Internal standard solution, Resolution solution, Standard preparation, Assay preparation, and Chromatographic system— Prepare as directed in the Assay.

Procedure— Proceed as directed for Procedure in the Assay. Calculate the ratio of cefuroxime axetil diastereoisomer A to the sum of the cefuroxime axetil diastereoisomers A and B taken by the formula: in which rA and rB are the peak responses of the cefuroxime axetil diastereoisomers A and B, respectively: between 0.48 and 0.55 is obtained.

0.2 M Monobasic ammonium phosphate— Dissolve 23.0 g of monobasic ammonium phosphate in water to obtain 1000 mL of solution.

Mobile phase— Prepare a suitable filtered and degassed mixture of 0.2 M Monobasic ammonium phosphate and methanol (620: 380). Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard solution— Prepare a solution of acetanilide in methanol containing 5.4 mg per mL.

Resolution solution— In a 50-mL volumetric flask, mix 10.0 mL of a solution of USP Cefuroxime Axetil RS in methanol containing 1.2 mg per mL, 5.0 mL of Internal standard solution, and 3.8 mL of a solution of USP Cefuroxime Axetil Delta-3 Isomers RS in methanol containing 0.16 mg per mL. Dilute with 0.2 M Monobasic ammonium phosphate to volume, and mix.

Standard preparation— Transfer about 30 mg of USP Cefuroxime Axetil RS, accurately weighed, to a 25-mL volumetric flask, dissolve in methanol, dilute with methanol to volume, and mix. Promptly transfer 10.0 mL of this solution to a 50-mL volumetric flask, add 5.0 mL of Internal standard solution and 3.8 mL of methanol, dilute with 0.2 M Monobasic ammonium phosphate to volume, and mix. [note—Use this Standard preparation promptly, or refrigerate and use on the day prepared.]

Assay preparation— Transfer about 30 mg of Cefuroxime Axetil to a 25-mL volumetric flask, dissolve in methanol, dilute with methanol to volume, and mix. Promptly transfer 10.0 mL of this solution to a 50-mL volumetric flask, add 5.0 mL of Internal standard solution and 3.8 mL of methanol, dilute with 0.2 M Monobasic ammonium phosphate to volume, and mix. [note—Use this Assay preparation promptly, or refrigerate and use on the day prepared.]

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 278-nm detector and a 4.6- mm × 25-cm column containing 5-µm packing L13. The flow rate is about 1.5 mL per minute. Chromatograph the Resolution solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.4 for acetanilide, 0.8 for cefuroxime axetil diastereoisomer B, 0.9 for cefuroxime axetil diastereoisomer A, and 1.0 for cefuroxime axetil delta-3 isomers; the resolution, R, between cefuroxime axetil diastereoisomer A and B is not less than 1.5; and the resolution, R, between cefuroxime axetil diastereoisomer A and cefuroxime axetil delta-3 isomers is not less than 1.5. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency is not less than 3000 theoretical plates when measured using the cefuroxime axetil diastereoisomer A peak; and the relative standard deviation for replicate injections is not more than 2.0%.

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 µg, of cefuroxime (C16H16N4O8S) in each mg of Cefuroxime Axetil taken by the formula: in which WS is the weight, in mg, of USP Cefuroxime Axetil RS taken to prepare the Standard preparation; WU is the weight, in mg, of Cefuroxime Axetil taken to prepare the Assay preparation; PS is the designated cefuroxime (C16H16N4O8S) content, in µg per mg, of anhydrous USP Cefuroxime Axetil RS; K is the percentage water content of USP Cefuroxime Axetil RS; and RU and RS are the ratios of the sum of the peak responses of the cefuroxime axetil diastereoisomers A and B to the peak response of the internal standard obtained from the Assay preparation and the Standard preparation, respectively.