A: Infrared Absorption á197Kñ.

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.

Test solution: 5mg per mL,in alcohol.

Mobile phase— Proceed as directed in the Assay.

Standard stock solution— Prepare as directed for Standard preparationin the Assay.

Standard solution— Transfer 0.5mLof the Standard stock solutionto a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.

Test solution— Prepare as directed for Assay preparation.

Chromatographic system (see Chromatography á621ñ)— Prepare as directed in the Assay.Chromatograph the Standard stock solution,and record the peak responses as directed for Procedure:the column efficiency is not less than 6000theoretical plates;and the relative standard deviation for replicate injections is not more than 2.0%.Chromatograph the Test solution,and record the peak responses as directed for Procedure:the resolution,R,between dinoprostone and any other adjacent peak is not less than 1.0.

Procedure— Separately inject equal volumes (about 20µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the peak responses.Calculate the percentage of each impurity in the portion of Dinoprostone taken by the formula: in which Cis the concentration,in µg per mL,of USP Dinoprostone RSin the Standard solution;Wis the weight,in mg,of Dinoprostone taken to prepare the Test solution;Fis the relative response factor (see Table 1for values);riis the peak response for each impurity obtained from the Test solution;and rSis the peak response for dinoprostone obtained from the Standard solution.

Mobile phase— Prepare a filtered and degassed mixture of methanol and 0.2%acetic acid (58:42).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Dinoprostone RSin Mobile phase,and dilute quantitatively,and stepwise if necessary,with Mobile phaseto obtain a solution having a known concentration of about 2.5mg per mL.

Assay preparation— Transfer about 25.0mg of Dinoprostone,accurately weighed,to a 10-mLvolumetric flask,dissolve in and dilute with Mobile phaseto volume,and mix.

Chromatographic system (see Chromatography á621ñ)— The liquid chromatograph is equipped with a 210-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1mLper minute.The column temperature is maintained at 30.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between dinoprostone and any other adjacent peak is not less than 1.0;and the relative standard deviation for replicate injections is not more than 2.0%.

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 C20H32O5in the portion of Dinoprostone taken by the formula: in which Cis the concentration,in mg per mL,of USP Dinoprostone RSin the Standard preparation;and rUand rSare the peak responses obtained from the Assay preparationand the Standard preparation,respectively.