A: Infrared Absorption á197Kñ.

B: The chromatogram of the Assay preparation obtained as directed in the Assayexhibits a major peak for ceftriaxone,the retention time of which corresponds to that exhibited in the chromatogram of the Standard preparationobtained as directed in the Assay.

C: It responds to the tests for Sodium á191ñ.

pH7.0buffer— Dissolve 13.6g of dibasic potassium phosphate and 4.0g of monobasic potassium phosphate in water to obtain 1000mLof solution.Adjust this solution with phosphoric acid or 10Npotassium hydroxide to a pHof 7.0±0.1.

pH5.0buffer— Dissolve 25.8g of sodium citrate in 500mLof water,adjust with citric acid solution (1in 5)to a pHof 5.0±0.1,and dilute with water to a volume of 1000mL.

Mobile phase— Dissolve 3.2g of tetraheptylammonium bromide in 400mLof acetonitrile,add 44mLof pH7.0bufferand 4mLof pH5.0buffer,and add water to make 1000mL.Filter through a membrane filter of 0.5µm or finer porosity,and degas.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Ceftriaxone Sodium RSin Mobile phase,to obtain a solution having a known concentration of about 0.2mg per mL.Use this solution promptly after preparation.

Resolution solution— Dissolve a suitable quantity of USP Ceftriaxone Sodium E-Isomer RSin Standard preparation,and dilute with Mobile phaseto obtain a solution containing about 160µg of USP Ceftriaxone Sodium E-Isomer RSper mLand 160µg of USP Ceftriaxone Sodium RSper mL.Use this solution promptly after preparation.

Assay preparation— Transfer about 40mg of Ceftriaxone Sodium,accurately weighed,to a 200-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.Use this solution promptly after preparation.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 270-nm detector and a 4.0-mm ×15-cm column that contains 5-µm packing L1.The flow rate is about 2mLper minute.Chromatograph the Resolution solution,and record the peak responses as directed under Procedure:the resolution,R,between the ceftriaxone E-isomer and ceftriaxone peaks is not less than 3.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 1500theoretical plates,the tailing factor for the analyte peak is not more than 2,and the relative standard deviation for replicate injections is not more than 2%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in µg,of ceftriaxone (C18H18N8O7S3)per mg of the Ceftriaxone Sodium taken by the formula: in which Cis the concentration,in mg per mL,of USP Ceftriaxone Sodium RSin the Standard preparation,Pis the designated potency,in µg of ceftriaxone per mg,of USP Ceftriaxone Sodium RS,Wis the quantity,in mg,of the Ceftriaxone Sodium taken to prepare the Assay preparation,and rUand rSare the ceftriaxone peak responses obtained from the Assay preparationand the Standard preparation,respectively.