Mobile phase— Prepare a filtered and degassed mixture of 0.01Mtetrabutylammonium hydrogen sulfate and acetonitrile (86:14).Make adjustments if necessary (seeSystem SuitabilityunderChromatography á621ñ).

Standard solution— Dissolve an accurately weighed quantity of USP Alfentanil Hydrochloride RSinMobile phase,and dilute quantitatively,and stepwise if necessary,withMobile phase to obtain a solution having a known concentration of about 0.54mg per mL.

Test solution— Transfer about 54mg of Alfentanil Hydrochloride,accurately weighed,to a 100-mLvolumetric flask,dilute withMobile phase to volume,and mix.

Chromatographic system(see Chromatography á621ñ)— The liquid chromatograph is equipped with a 235-nm detector and a 4.6-mm ×25-cm column that contains spherical 5-µm packing L1.The flow rate is about 2mLper minute.Chromatograph theStandard solution,and record the peak responses as directed underProcedure:the column efficiency is not less than 5400theoretical plates,the tailing factor is not more than 1.3,and the relative standard deviation for replicate injections is not more than 1.0%.

Procedure— Inject a volume (about 25µL)of theTest solution into the chromatograph,record the chromatogram,and measure the responses for all of the peaks.Calculate the percentage of each impurity in the portion of Alfentanil Hydrochloride taken by the formula: in whichriis the response of each impurity peak,andrsis the sum of all of the peaks:not more than 0.5%of any single impurity is found,and the sum of all impurities is not more than 1.0%.