(dye eth'' il stil bes' trol).
Phenol 4,4¢-(1,2-diethyl-1,2-ethenediyl)bis-, (E)-.
» Diethylstilbestrol contains not less than 97.0 percent and not more than 100.5 percent of C18H20O2, calculated on the dried basis.
Packaging and storage Preserve in tight, light-resistant containers. Store at room temperature.
USP Reference standards 11
A: Ultraviolet Absorption 197U
Solution: 10 µg per mL.
Absorptivities at 230 to 350 nm do not differ by more than 3.0%.
B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
Melting range 741: between 169 and 175, but the range between beginning and end of melting does not exceed 4.
Acidity or alkalinity A solution of 100 mg in 5 mL of neutralized 70% alcohol is neutral to litmus.
Loss on drying 731 Dry it at 105 for 2 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.05%.
Diluent Prepare a mixture of alcohol and water (1:1).
Mobile phase Prepare a filtered and degassed mixture of methanol and water (3:1). Make adjustments if necessary (see System Suitability under Chromatography 621).
Standard preparation Dissolve an accurately weighed quantity of USP Diethylstilbestrol RS in Diluent, and dilute quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 20 µg per mL.
System suitability solution Dissolve 10 mg of USP Diethylstilbestrol RS in 50 mL of chloroform, and allow the solution to stand in the dark for not less than 5 hours. Pipet 5.0 mL of this solution into a 50-mL volumetric flask, and evaporate to dryness under a current of air. Dissolve the residue (the cis- and trans-isomers of diethylstilbestrol) in Diluent, sonicating if necessary. Dilute with Diluent to volume, and mix.
Assay preparation Dissolve an accurately weighed quantity of Diethylstilbestrol in Diluent, and dilute quantitatively, and stepwise if necessary, with Diluent to obtain a solution having a concentration of about 20 µg per mL.
Chromatographic system (see Chromatography 621) The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 1.00 for trans-diethylstilbestrol and 1.33 for cis-diethylstilbestrol; and the resolution, R, between trans-diethylstilbestrol and cis-diethylstilbestrol is not less than 4.0. Chromatograph the Standard preparation, and record the peak responses for the trans-isomer as directed for Procedure: the column efficiency is not less than 3000 theoretical plates; the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure Separately inject equal volumes (about 50 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the areas of the peak responses for the cis- and trans-isomers of diethylstilbestrol. Calculate the quantity, in µg, of C18H20O2 in the portion of Diethylstilbestrol taken by the formula:
C(rt, U + 1.26rc, U) / (rt,S + 1.26rc, S)in which C is the concentration, in µg per mL, of USP Diethylstilbestrol RS in the Standard preparation; and rt, U and rt, S are the peak responses for the trans-isomer obtained from the Assay preparation and the Standard preparation, respectively; and rc, U and rc,S are the peak responses for the cis-isomer obtained from the Assay preparation and the Standard preparation, respectively.
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USP35NF30 Page 2895Pharmacopeial Forum: Volume No. 29(5) Page 1463