A: It responds to the Thin-layer Chromatographic Identification Test á201ñ,a test solution of it diluted,if necessary,with water,to obtain a concentration of 0.5mg of alfentanil per mL.Prepare a Standard solution in water to obtain a concentration of 0.54mg per mLof USP Alfentanil Hydrochloride RS.Apply 200µLeach of the Standard solution and the test solution,develop the plate using a solvent system consisting of a mixture of chloroform,methanol,and formic acid (85:10:5),and visualize the spots using Dragendorff's reagent.

B: 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.

Mobile phase and Chromatographic system— Proceed as directed in the test for Chromatographic purityunder Alfentanil Hydrochloride.

Standard solution— Use the Standard preparationas obtained in the Assay.

Test solution— Use the Assay preparation.

Procedure— Inject a volume (about 25µL)of the Test solutioninto the chromatograph,record the chromatogram,and measure the responses for all of the peaks.Calculate the percentage of each impurity in the portion of Injection taken by the formula: in which riis the response of each impurity peak,and rsis the sum of all of the peaks:the sum of all the impurities is not more than 2.0%.

Mobile phase and Chromatographic system— Proceed as directed in the test for Chromatographic purityunder Alfentanil Hydrochloride.

Standard preparation— Dissolve an accurately weighed quantity of USP Alfentanil Hydrochloride RSin saline TS,and dilute quantitatively,and stepwise if necessary,with saline TSto obtain a solution having a known concentration of about 0.54mg per mL.

Assay preparation— Transfer an accurately measured volume of Injection to a suitable container,and dilute with saline TS,if necessary,to obtain a concentration of about 0.50mg per mLof alfentanil.

Procedure— Separately inject equal volumes (about 25µL)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 C21H32N6O3in each mLof the Injection taken by the formula: in which 416.52and 452.98are the molecular weights of alfentanil and alfentanil hydrochloride,respectively;Cis the concentration,in mg per mL,of USP Alfentanil Hydrochloride RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.