Test solution: 50 mg per mL.

Mobile phase— Prepare a filtered and degassed mixture of 0.05 M monobasic ammonium phosphate, previously adjusted with 10% (v/v) phosphoric acid to a pH of 2.5 ± 0.1, and methanol (60:40). Make adjustments if necessary (see System Suitability under Chromatography 621).

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

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

Chromatographic system (see Chromatography 621)—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 1 mL per 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 1750 theoretical 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 10 µL) of the Standard solution and the Test solution into 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 C is the concentration, in µg per mL, of USP Chloramphenicol RS in the Standard solution; W is the quantity, in mg, of Chloramphenicol Sodium Succinate taken to prepare the Test solution; Q is the quantity, in µg, of chloramphenicol in each mg of Chloramphenicol Sodium Succinate taken, as obtained in the Assay; and rU and rS are the peak areas obtained from the Test solution and the Standard solution, respectively. Not more than 2.0% is found.

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

Procedure— Concomitantly determine the absorbance of the Standard preparation, at the wavelength of maximum absorbance at about 278 nm, and the absorbance of the Assay preparation, at the wavelength of maximum absorbance at about 276 nm, 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 C is the concentration, in µg per mL, of USP Chloramphenicol RS in the Standard preparation; P is the potency, in µg per mg, of USP Chloramphenicol RS; W is the weight, in µg, of Chloramphenicol Sodium Succinate taken in each mL of the Assay preparation; and AU and AS are the absorbances of the Assay preparation and the Standard preparation, respectively.