Mobile phase— Prepare a mixture of water,methanol,and 0.2Mmonobasic ammonium phosphate (33:5:3).Pass through a filter having a 0.5-µm or finer porosity,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Cefonicid Sodium RSin Mobile phaseto obtain a solution having a known concentration of about 200µg of cefonicid (C18H18N6O8S3)per mL.

Assay preparation 1 (where it is represented as being in a single-dose container)—Constitute Cefonicid 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 quantitatively dilute with Mobile phaseto obtain a solution containing about 200µg of cefonicid per mL.

Assay preparation 2 (where the label states the quantity of cefonicid in a given volume of constituted solution)—Constitute Cefonicid for Injection in a volume of water,accurately measured,corresponding to the volume of solvent specified in the labeling.Quantitatively dilute an accurately measured volume of the constituted solution with Mobile phaseto obtain a solution containing about 200µg of cefonicid per mL.

Resolution solution— Dissolve a quantity of USP Cefonicid Sodium RSin Mobile phaseto obtain a solution containing about 0.2mg per mL.Heat on a steam bath for 30minutes,and cool.This Resolution solutioncontains a mixture of cefonicid and desacetyl cefonicid.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L1.The flow rate is about 2mLper minute.Chromatograph the Standard preparationand the Resolution solution,and record the peak responses as directed for Procedure:the column efficiency determined from the analyte peak is not less than 1500theoretical plates,the tailing factor for the analyte peak is not more than 1.3,the resolution R,between the cefonicid and the desacetyl cefonicid peaks is not less than 1.1;the column efficiency determined from the analyte peak is not less than 1500theoretical plates;the tailing factor for the analyte peak is not more than 2.0;and the relative standard deviation for replicate injections of the Standard preparationis not more than 2%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of cefonicid (C18H18N6O8S3)withdrawn from the container,or in the portion of constituted solution taken by the formula: in which Lis the labeled quantity,in mg,of cefonicid (C18H18N6O8S3)in the container,or in the volume of constituted solution taken;Dis the concentration,in µg per mLof cefonicid (C18H18N6O8S3)in Assay preparation 1or Assay preparation 2,based on the labeled quantity in the container or in the portion of constituted solution taken,respectively,and the extent of dilution;and rUand rSare the peak responses obtained from the relevant Assay preparationand the Standard preparation,respectively.