A: Infrared Absorption á197Kñ.

B: It responds to the tests for Sodium á191ñ.

Mobile phase— Prepare a buffer of 0.0009Mtetrabutylammonium hydrogen phosphate and 0.05Mdibasic sodium phosphate as follows.Dissolve 604mg of tetrabutylammonium phosphate and 26.8g of dibasic sodium phosphate in 1800mLof water,adjust with phosphoric acid to a pHof 3.8,and dilute with water to 2000mL.Prepare a filtered and degassed mixture of this buffer and acetonitrile (116:84),allow to stand for 1hour,and if necessary readjust with phosphoric acid to a pHof 3.8.Make any necessary adjustments (see System Suitabilityunder Chromatography á621ñ).

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

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

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

Chromatographic system (see Chromatography á621ñ)—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 2mLper 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 25µL)of the Standard preparationand the Assay preparationinto 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 Cis the concentration,in mg per mL,of USP Carbenicillin Indanyl Sodium RS,calculated on the anhydrous basis,in the Standard preparation,Pis the assigned potency,in µg per mg,of USP Carbenicillin Indanyl Sodium RS,Wis the quantity,in mg,of Carbenicillin Indanyl Sodium taken to prepare the Assay preparation,and rUand rSare the carbenicillin indanyl peak responses obtained from the Assay preparationand the Standard preparation,respectively.