Estriol, chemical structure, molecular formula, Reference Standards

Estriol

C18H24O3 288.38

Estra-1,3,5(10)-triene-3,16,17-triol,(16a,17b)-.
Estriol [50-27-1].

»Estriol contains not less than 97.0percent and not more than 102.0percent of C18H24O3,calculated on the dried basis.

Packaging and storage— Preserve in tight containers.

USP Reference standards á11ñ— USP Estriol RS.

Completeness of solution— Dissolve 500mg in 10mLof pyridine:the solution is clear and free from undissolved solid.

Identification—

A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

Solution: 100µg per mL.

Medium: alcohol.

Specific rotation á781Sñ: between +54

and +62

Test solution: 4mg per mL,in dioxane.

Loss on drying á731ñ— Dry it at 105

for 3hours:it loses not more than 0.5%of its weight.

Residue on ignition á281ñ: not more than 0.1%.

Chromatographic purity—

Test preparation— Prepare a solution of Estriol in a mixture of dioxane and water (9:1)to obtain a solution containing 20.0mg per mL.

Standard solution andStandard dilutions— Prepare a solution of USP Estriol RSin a mixture of dioxane and water (9:1)to obtain a solution containing 20mg per mL(Standard solution).Prepare a series of dilutions of the Standard solutionin a mixture of dioxane and water (9:1)to obtain solutions containing 0.40,0.20,0.10,and 0.05mg per mL(Standard dilutions).

Chromatographic chamber— Line a suitable chamber (see Chromatography á621ñ)with absorbent paper,and pour into the chamber 200mLof developing solvent,prepared by mixing,just prior to use,90mLof chloroform,5mLof methanol,5mLof acetone,and 5mLof acetic acid.Equilibrate the chamber for 15minutes before using.

Procedure— Apply 5-µLvolumes of the Test preparation,Standard solution,and each of the four Standard dilutionsat equidistant points along a line 2.5cm from one edge of a 20-×20-cm thin-layer chromatographic plate (see Chromatography á621ñ)coated with a 0.25-mm layer of chromatographic silica gel mixture.Place the plate in the Chromatographic chamber,seal the chamber,and allow the chromatogram to develop until the solvent front has moved 15cm above the line of application.Remove the plate,and allow the solvent to evaporate.Spray the plate with a mixture of methanol and sulfuric acid (7:3),then heat the plate at 100

for 15minutes.The lane of the Test preparationexhibits its principal spot at the same RFvalue as the principal spot of the Standard solution.If spots other than the principal spot are observed in the lane of the Test preparation,estimate the concentration of each by comparison with the Standard dilutions.The spots from the 0.40-,0.20-,0.10-,and 0.05-mg-per-mLdilutions are equivalent to 2.0%,1.0%,0.5%,and 0.25%of impurities,respectively.The requirements of the test are met if the sum of impurities in the Test preparationis not greater than 2.0%.

Assay— Dissolve about 50mg of Estriol,accurately weighed,in alcohol to make 100.0mL,and mix.Dilute 10.0mLof this solution with alcohol to 100.0mL.Similarly,dissolve a suitable quantity of USP Estriol RS,accurately weighed,in alcohol to obtain a Standard solution having a known concentration of about 50µg per mL.Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 281nm.Calculate the quantity,in mg,of C18H24O3in the portion of Estriol taken by the formula:

C(AU/AS),

in which Cis the concentration,in µg per mL,of USP Estriol RSin the Standard solution,and AUand ASare the absorbances of the solution of Estriol and the Standard solution,respectively.

Auxiliary Information— Staff Liaison:Clydewyn M.Anthony,Ph.D.,Scientist

Expert Committee:(PA1)Pharmaceutical Analysis 1

USP28–NF23Page 776

Phone Number:1-301-816-8139