A: Infrared Absorption 197K.

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

C: It responds to the tests for Sodium 191.

(Official January 1, 2007)

pH 7.0 Buffer— Dissolve 13.6 g of dibasic potassium phosphate and 4.0 g of monobasic potassium phosphate in water to obtain 1000 mL of solution. Adjust this solution with phosphoric acid or 10 N potassium hydroxide to a pH of 7.0 ± 0.1.

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

Mobile phase— Dissolve 3.2 g of tetraheptylammonium bromide in 400 mL of acetonitrile, add 44 mL of pH 7.0 Buffer and 4 mL of pH 5.0 Buffer, and add water to make 1000 mL. Filter through a membrane filter of 0.5 µm or finer porosity, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

Resolution solution— Dissolve a suitable quantity of USP Ceftriaxone Sodium E-Isomer RS in Standard preparation, and dilute with Mobile phase to obtain a solution containing about 160 µg of USP Ceftriaxone Sodium E-Isomer RS per mL and 160 µg of USP Ceftriaxone Sodium RS per mL. Use this solution promptly after preparation.

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

Chromatographic system (see Chromatography 621)—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 2 mL per 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 1500 theoretical 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 20 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 ceftriaxone (C18H18N8O7S3) per mg of the Ceftriaxone Sodium taken by the formula: in which C is the concentration, in mg per mL, of USP Ceftriaxone Sodium RS in the Standard preparation; P is the designated potency, in µg of ceftriaxone per mg, of USP Ceftriaxone Sodium RS; W is the quantity, in mg, of the Ceftriaxone Sodium taken to prepare the Assay preparation; and rU and rS are the ceftriaxone peak responses obtained from the Assay preparation and the Standard preparation, respectively.