Chloramphenicol Palmitate
C27H42Cl2N2O6 561.54

Hexadecanoic acid,2-[(2,2-dichloroacetyl)amino]-3-hydroxy-3-(4-nitrophenyl)propyl ester,[R-(R*,R*)]-.
D-threo-(-)-2,2-Dichloro-N-[b-hydroxy-a-(hydroxymethyl)-p-nitrophenethyl]acetamide a-palmitate [530-43-8].
»Chloramphenicol Palmitate has a potency equivalent to not less than 555µg and not more than 595µg of chloramphenicol (C11H12Cl2N2O5)per mg.
Packaging and storage— Preserve in tight containers.
Identification— The retention time of the chloramphenicol palmitate peak in the chromatogram of the Assay preparationcorresponds to that of the chloramphenicol palmitate peak in the chromatogram of the Standard preparationas obtained in the Assay.
Melting range á741ñ: between 87and 95.
Specific rotation á781Sñ: between +21and +25.
Test solution: 50mg,undried,per mL,in dehydrated alcohol.
Crystallinity á695ñ: meets the requirements.
Loss on drying á731ñ— Dry it to constant weight over phosphorus pentoxide in vacuum at a pressure not exceeding 5mm of mercury:it loses not more than 0.5%of its weight.
Acidity— Dissolve 1.0g by heating at 35with 5mLof a 1:1mixture of 80percent alcohol and ether,previously neutralized using phenolphthalein TS.Titrate with 0.1Nsodium hydroxide VS,using phenolphthalein TS,until on gentle shaking a pink color persists for not less than 30seconds:not more than 0.4mLis consumed.
Free chloramphenicol— Dissolve 1.0g in 80mLof xylene with the aid of gentle warming.Cool,and extract with three 15-mLportions of water,combining the aqueous extracts and discarding the xylene.Dilute the combined aqueous extracts with water to 50mL,extract with 10mLof toluene,allow to separate,and discard the toluene.Centrifuge a portion of the aqueous solution,and determine the absorbance of the clear solution at the wavelength of maximum absorbance at about 278nm,using a suitable spectrophotometer,and using as a reagent blank to set the instrument to zero the solution obtained by the same procedure without the specimen:the absorbance is not more than 0.268(0.045%).
Assay—
Mobile phase— Prepare a suitable degassed mixture of methanol,water,and glacial acetic acid (172:27:1).
Standard preparation— Transfer about 65mg of USP Chloramphenicol Palmitate RSto a 50-mLvolumetric flask,add about 40mLof methanol and 1mLof glacial acetic acid,and sonicate for a few minutes.Dilute with methanol to volume,and mix.Transfer 10.0mLof this solution to a 25-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
Assay preparation— Using about 65mg of Chloramphenicol Palmitate,accurately weighed,prepare as directed under Standard preparation.
Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 280-nm detector and a 3.9-mm ×30-cm column that contains 10-µm packing L1.The flow rate is about 2mLper minute.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 2400theoretical plates,and the relative standard deviation for replicate injections is not more than 0.5%.
Procedure— Separately inject equal volumes (about 10µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in µg,of chloramphenicol (C11H12Cl2N2O5)equivalent in each mg of specimen taken by the formula:
(WS/WU)(PS)(rU/rS),
in which WSand WUare the quantities,in mg,of USP Chloramphenicol Palmitate RSand Chloramphenicol Palmitate taken,respectively,PSis the designated chloramphenicol equivalent,in µg per mg,of USP Chloramphenicol Palmitate RS,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:William W.Wright,Ph.D.,Scientific Fellow
Expert Committee:(PA7)Pharmaceutical Analysis 7
USP28–NF23Page 433
Phone Number:1-301-816-8335