A: Infrared Absorption 197K.

B: It responds to the tests for Sodium 191.

(Official January 1, 2007)

Mobile phase— Prepare a buffer of 0.0009 M tetrabutylammonium hydrogen phosphate and 0.05 M dibasic sodium phosphate as follows. Dissolve 604 mg of tetrabutylammonium phosphate and 26.8 g of dibasic sodium phosphate in 1800 mL of water, adjust with phosphoric acid to a pH of 3.8, and dilute with water to 2000 mL. Prepare a filtered and degassed mixture of this buffer and acetonitrile (116:84), allow to stand for 1 hour, and if necessary readjust with phosphoric acid to a pH of 3.8. Make any necessary adjustments (see System Suitability under Chromatography 621).

Diluting solvent— Prepare a mixture of acetonitrile and 0.005 M monobasic potassium phosphate (85:15).

Standard preparation— Dissolve an accurately weighed quantity of USP Carbenicillin Indanyl Sodium RS quantitatively in Diluting solvent to obtain a solution having a known concentration of about 250 µg per mL. This Standard preparation contains the equivalent of about 222 µg of carbenicillin (C17H18N2O6S) per mL.

Assay preparation— Transfer about 125 mg of Carbenicillin Indanyl Sodium, accurately weighed, to a 50-mL volumetric flask, dissolve in Diluting solvent with the aid of sonication, dilute with Diluting solvent to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with Diluting solvent to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 210-nm detector and a 4.6-mm × 25-cm column that contains packing L7. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 25 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas of the responses for the major peaks. Calculate the quantity, in µg, of carbenicillin (C17H18N2O6S) in each mg of the Carbenicillin Indanyl Sodium taken by the formula: in which C is the concentration, in mg per mL, of USP Carbenicillin Indanyl Sodium RS, calculated on the anhydrous basis, in the Standard preparation; P is the assigned potency, in µg per mg, of USP Carbenicillin Indanyl Sodium RS; W is the quantity, in mg, of Carbenicillin Indanyl Sodium taken to prepare the Assay preparation; and rU and rS are the carbenicillin indanyl peak responses obtained from the Assay preparation and the Standard preparation, respectively.