Mobile phase ,Diluting solvent,System suitability preparation,and Chromatographic system—Prepare as directed in the Assay.

Ferric chloride solution— Transfer 4mLof ferric chloride TSto a 100-mLvolumetric flask,dilute with water to volume,and mix.

Identification solution— Dissolve 10mg of naloxone in 100mLof 0.1Nhydrochloric acid.Transfer 10.0mLof this solution to a 100-mLvolumetric flask,and add 0.5mLof Ferric chloride solution.Heat on a steam bath for 10minutes,cool,dilute with water to volume,and mix.

Standard solution— Transfer 2.0mLof the Standard preparationprepared as directed in the Assayto a 100-mLvolumetric flask,dilute with Diluting solventto volume,and mix.

Test solution— Use the Assay preparation.

Procedure— Separately inject equal volumes (about 100µL)of the Identification solution,the Standard solution,and the Test solutioninto the chromatograph,record the chromatograms,and measure the areas of the peak responses for naloxone and 2,2¢-bisnaloxone.The relative retention times are about 2.8for the naloxone dimer and 1.0for naloxone.Calculate the percentage of 2,2¢-bisnaloxone in the volume of Injection taken by the formula: in which Lis the labeled quantity,in µg per mL,of naloxone hydrochloride (C19H21NO4·HCl)in the Injection taken,363.84and 327.38are the molecular weights of anhydrous naloxone hydrochloride and naloxone,respectively,Cis the concentration,in µg per mL,of USP Naloxone RSin the Standard solution,1.8is the ratio of UVabsorptivity of 2,2¢-bisnaloxone to that of naloxone hydrochloride,Vbis the volume,in mL,of the Test solution,Vis the volume,in mL,of Injection taken,rUis the peak response for 2,2¢-bisnaloxone obtained from the Test solution,and rSis the peak response for naloxone obtained from the Standard solution.Not more than 4.0%is found.

Mobile phase— Prepare a filtered and degassed mixture of 1.36g of sodium 1-octanesulfonate,1.0g of sodium chloride,580mLof water,420mLof methanol,and 1.0mLof phosphoric acid.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Diluting solvent— Transfer 150mg of edetate disodium to a 2000-mLvolumetric flask,and add 0.9mLof hydrochloric acid.Dilute with water to volume,and mix.

Standard preparation— Dissolve an accurately weighed quantity of USP Naloxone RSin Diluting solvent,and dilute quantitatively,and stepwise if necessary,with Diluting solventto obtain a solution having a known concentration of about 10µg per mL.

Assay preparation 1 (for Injection labeled to contain not more than 100µg of naloxone hydrochloride per mL)—Transfer an accurately measured volume of Injection,equivalent to about 100µg of naloxone hydrochloride,to a 10-mLvolumetric flask,add Diluting solventto volume,and mix.

Assay preparation 2 (for Injection labeled to contain more than 100µg of naloxone hydrochloride per mL)—Transfer an accurately measured volume of Injection,equivalent to about 2000µg of naloxone hydrochloride,to a 200-mLvolumetric flask,add Diluting solventto volume,and mix.

System suitability preparation— Prepare a solution in Diluting solventcontaining about 20µg of USP Naloxone RSand about 2.5µg of acetaminophen per mL.

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 229-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1mLper minute.Chromatograph the Standard preparation(about 100µL)and the System suitability preparation(about 20µL),and record the peak responses as directed under Procedure:the resolution,R,between the acetaminophen and naloxone peaks is not less than 8,and the relative standard deviation for replicate injections of the Standard preparationis not more than 1.5%.

Procedure— [NOTE—Use peak areas where peak responses are indicated.]Separately inject equal volumes (about 100µL)of the Standard preparationand the appropriate Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are about 0.5for acetaminophen and 1.0for naloxone.Calculate the quantity,in µg,of C19H21NO4·HCl in each mLof the Injection taken by the formula: in which 363.84and 327.38are the molecular weights of anhydrous naloxone hydrochloride and naloxone,respectively,Vais the volume,in mL,of the Assay preparation,Cis the concentration,in µg per mL,of USP Naloxone RSin the Standard preparation,Vis the volume,in mL,of Injection taken,and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.