A:Infrared Absorption á197Kñ— Do not dry specimens.

B:Acid solvent— The UVabsorption spectrum of a solution in 0.1Nhydrochloric acid (1in 3000)exhibits maxima and minima at the same wavelengths as that of a similar solution of USP Ketamine Hydrochloride RS,concomitantly measured,and the respective absorptivities,at the wavelengths of maximum absorbance at about 269and 276nm,do not differ by more than 3.0%.

Mobile phase— Dissolve 0.95g of sodium 1-hexanesulfonate in 1Lof a solution consisting of a mixture of water and acetonitrile (3:1).Add 4mLof acetic acid,and mix.

Standard solution— Dissolve accurately weighed quantities of USP Ketamine Hydrochloride RSand USP Ketamine Related Compound A RSin Mobile phase (sonicate if necessary)to prepare a solution containing about 0.005mg per mLof each compound.Prepare immediately before use.

Test solution— Transfer an accurately weighed quantity of about 50.0mg of Ketamine Hydrochloride to a 50-mLvolumetric flask.Dissolve in and dilute withMobile phase to volume,sonicating if necessary.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 215-nm detector and a 4.0-mm ×4.0-mm guard column with a 4.0-mm ×12.5-cm analytical column that contains 5-µm packing L1.The flow rate is about 1.0mLper minute.Chromatograph the Standard solution,and record the peak responses as directed forProcedure:the order of elution is ketamine hydrochloride followed by ketamine related compound A;the resolution,R,between these two peaks is not less than 2.0;the retention time of ketamine hydrochloride is between 3.0and 4.5minutes (if necessary,adjust the concentration of water and acetonitrile);and the tailing factor is not greater than 1.5.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solution and theTest solution into the chromatograph,record the chromatograms,identify the ketamine hydrochloride and ketamine related compound Apeaks,and measure the areas of the major peaks.Calculate the area percentage of each impurity,relative to ketamine hydrochloride,in the portion of Ketamine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Ketamine Hydrochloride RSin the Standard solution;Wis the weight,in mg,of Ketamine Hydrochloride taken to prepare the Test solution;riis the peak area of each individual impurity peak in the Test solution;and rSis the response of the ketamine hydrochloride peak obtained from the Standard solution.Not more than 0.1%of ketamine related compound Ais found;the response of no other unknown impurity is greater than 0.3%of the ketamine peak area;and the sum of the responses of all unknown impurity peaks is not greater than 1.0%of the ketamine peak response.

Buffer— Dissolve 5.75g of monobasic ammonium phosphate in 1000mLof water.Add 6mLof triethylamine,and adjust with phosphoric acid to a pHof 3.0.

Mobile phase— Prepare a filtered and degassed mixture of Bufferand methanol (65:35).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

System suitability solution— Transfer about 12.5mg each,of USP Ketamine Hydrochloride RSand USP Ketamine Related Compound A RS,both accurately weighed,to a 50-mLvolumetric flask,dissolve in Mobile phasewith the aid of sonification if necessary,dilute with Mobile phaseto volume,and mix.Transfer 10.0mLof the solution so obtained to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Standard preparation— Transfer about 10mg of USP Ketamine Hydrochloride RS,accurately weighed,to a 50-mLvolumetric flask,add about 20mLof Mobile phase,and sonicate to dissolve.Dilute with Mobile phaseto volume,and mix.

Assay preparation— Transfer about 20mg of Ketamine Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,add about 35mLof Mobile phase,and sonicate to dissolve.Dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 220-nm detector and a 4.6-mm ×25-cm column that contains 5-µm packing L1.The flow rate is about 1.0mLper minute.Chromatograph the System suitability solution,and record the peak responses as directed for Procedure:the order of elution is ketamine followed by ketamine related compound A;the resolution,R,between ketamine and ketamine related compound Ais not less than 2.0;the column efficiency determined from the ketamine peak is not less than 9400theoretical plates;and the tailing factor determined from the ketamine peak is not more than 1.6.Chromatograph the Standard preparation,and record the ketamine peak response as directed for Procedure:the relative standard deviation for replicate injections is not more than 0.6%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of C13H16ClNO·HCl in the portion of Ketamine Hydrochloride taken by the formula: in which Cis the concentration,in mg per mL,of USP Ketamine Hydrochloride RSin the Standard preparation;and rUand rSare the ketamine peak responses obtained from the Assay preparationand the Standard preparation,respectively.