A:Infrared Absorption á197Kñ.

B:Ultraviolet Absorption á197Uñ—

C: Dissolve about 500mg in 5mLof water,and render the mixture alkaline with 1Nsodium hydroxide.Extract with three 5-mLportions of methylene chloride:the aqueous layer meets the requirements of the tests for Citrate á191ñ.

D: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Standard solution— Pipet 25µLof acetone into a 100-mLvolumetric flask,dilute with dimethylformamide to volume,and mix.

Test solution— Dissolve 100mg of Sufentanil Citrate,accurately weighed,in 2.0mLof dimethylformamide contained in a polytef-lined screw-cap vial.

Chromatographic system(see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 4-mm ×1.83-m glass column containing support S2.The carrier gas is nitrogen with a flow rate of about 50mLper minute.The injection port temperature and the detector temperature are both maintained at 230.The column temperature is maintained at 175.Inject the Standard solution,and record the peak responses as directed for Procedure:the relative standard deviation of the acetone peak responses for replicate injections is not more than 5%.

Procedure— Separately inject equal volumes (about 2µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses.[NOTE—After injecting the Test solution,wait about 25minutes to allow the sufentanil peak to completely elute from the column.]Calculate the percentage of acetone in the portion of Sufentanil Citrate taken by the formula: in which CSis the concentration,in mg per mL,of acetone in the Standard solution;CUis the concentration,in mg per mL,of sufentanil citrate in the Test solution;and rUand rSare the peak responses obtained from the Test solutionand the Standard solution,respectively.Not more than 0.5%of acetone is found.

Mobile phaseand Chromatographic system— Proceed as directed in the Assay.

Blank solution— Transfer 33.2mg of citric acid,accurately weighed,to a 50-mLvolumetric flask.Dilute with Mobile phaseto volume,and mix.

Test solution— Transfer about 7.5mg of Sufentanil Citrate to a 10-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Procedure— Separately inject equal volumes (about 100µL)of the Blank solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses.Calculate the percentage of each impurity,disregarding any peaks corresponding to those found in the Blank solution,in the portion of Sufentanil Citrate taken by the formula: in which riis the peak response for each impurity;and rsis the sum of the responses of all of the peaks:not more than 0.5%of any impurity is found,and the sum of all impurities is not more than 1.0%.

Mobile phase— Prepare a filtered and degassed mixture of methanol,0.13Mammonium acetate,and acetonitrile (45:31:24).Adjust with glacial acetic acid or ammonium hydroxide to a pHof 7.2.Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Sufentanil Citrate RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 0.075mg per mL.

Assay preparation— Transfer about 18.7mg of Sufentanil Citrate,accurately weighed,to a 25-mLvolumetric flask;dissolve in and dilute with Mobile phaseto volume;and mix.Transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 228-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the tailing factor is not more than 2,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 100µL)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 C22H30N2O2S·C6H8O7in the portion of Sufentanil Citrate taken by the formula: in which Cis the concentration,in mg per mL,of USP Sufentanil Citrate RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.