Test solution: 50mg per mL.

Mobile phase— Prepare a filtered and degassed mixture of 0.05Mmonobasic ammonium phosphate,previously adjusted with 10%(v/v)phosphoric acid to a pHof 2.5±0.1,and methanol (60:40).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard solution— Dissolve an accurately weighed quantity of USP Chloramphenicol RSin Mobile phaseto obtain a solution having a known concentration of about 6µg per mL.Pass this solution through a filter having a 0.5-µm or finer porosity,and use the filtrate.

Test solution— Transfer about 33mg of Chloramphenicol Sodium Succinate,accurately weighed,to a 50-mLvolumetric flask.Dilute with Mobile phaseto volume,and mix.Pass a portion of this solution through a filter having a 0.5-µm or finer porosity.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 275-nm detector and a 4.6-mm ×10-cm column that contains 5-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Test solution,and record the peak responses as directed for Procedure:the column efficiency determined from the two major peaks,chloramphenicol-1-succinate and chloramphenicol-3-succinate,is not less than 1750theoretical plates;the resolution,R,between the two peaks is not less than 2.0;and the tailing factor is not more than 1.2.Chromatograph the Standard solution,and record the peak areas as directed for Procedure:the relative standard deviation for replicate injections is not less than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the areas for the free chloramphenicol peaks.Calculate the percentage of free chloramphenicol (C11H12Cl2N2O5)in the portion of Chloramphenicol Sodium Succinate taken by the formula: in which Cis the concentration,in µg per mL,of USP Chloramphenicol RSin the Standard solution;Wis the quantity,in mg,of Chloramphenicol Sodium Succinate taken to prepare the Test solution;Qis the quantity,in µg,of chloramphenicol in each mg of Chloramphenicol Sodium Succinate taken,as obtained in the Assay;and rUand rSare the peak areas obtained from the Test solutionand the Standard solution,respectively.Not more than 2.0%is found.

Standard preparation— Dissolve an accurately weighed quantity of USP Chloramphenicol RSin water,and dilute quantitatively with water to obtain a solution having a known concentration of about 20µg per mL.

Assay preparation— Dissolve an accurately weighed quantity of Chloramphenicol Sodium Succinate in water,and dilute quantitatively with water to obtain a solution having a concentration equivalent to about 20µg of chloramphenicol per mL.

Procedure— Concomitantly determine the absorbance of the Standard preparation,at the wavelength of maximum absorbance at about 278nm,and the absorbance of the Assay preparation,at the wavelength of maximum absorbance at about 276nm,in 1-cm cells,with a suitable spectrophotometer,using water as the blank.Calculate the quantity,in µg,of chloramphenicol (C11H12Cl2N2O5)in each mg of Chloramphenicol Sodium Succinate taken by the formula: in which Cis the concentration,in µg per mL,of USP Chloramphenicol RSin the Standard preparation;Pis the potency,in µg per mg,of USP Chloramphenicol RS;Wis the weight,in µg,of Chloramphenicol Sodium Succinate taken in each mLof the Assay preparation;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.