(es' tree ol).
» Estriol contains not less than 97.0 percent and not more than 102.0 percent of C18H24O3, calculated on the dried basis.
Packaging and storage Preserve in tight containers.
USP Reference standards 11
Completeness of solution Dissolve 500 mg in 10 mL of pyridine: the solution is clear and free from undissolved solid.
B: Ultraviolet Absorption 197U
Solution: 100 µg per mL.
Specific rotation 781S: between +54 and +62.
Test solution: 4 mg per mL, in dioxane.
Loss on drying 731 Dry it at 105 for 3 hours: it loses not more than 0.5% of its weight.
Residue on ignition 281: not more than 0.1%.
Test preparation Prepare a solution of Estriol in a mixture of dioxane and water (9:1) to obtain a solution containing 20.0 mg per mL.
Standard solution and Standard dilutions Prepare a solution of USP Estriol RS in a mixture of dioxane and water (9:1) to obtain a solution containing 20 mg per mL (Standard solution). Prepare a series of dilutions of the Standard solution in a mixture of dioxane and water (9:1) to obtain solutions containing 0.40, 0.20, 0.10, and 0.05 mg per mL (Standard dilutions).
Chromatographic chamber Line a suitable chamber (see Chromatography 621) with absorbent paper, and pour into the chamber 200 mL of developing solvent, prepared by mixing, just prior to use, 90 mL of chloroform, 5 mL of methanol, 5 mL of acetone, and 5 mL of acetic acid. Equilibrate the chamber for 15 minutes before using.
Procedure Apply 5-µL volumes of the Test preparation, Standard solution, and each of the four Standard dilutions at equidistant points along a line 2.5 cm from one edge of a 20- × 20-cm thin-layer chromatographic plate (see Chromatography 621) 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 15 cm 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 15 minutes. The lane of the Test preparation exhibits its principal spot at the same RF value 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-mL dilutions 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 preparation is not greater than 2.0%.
Assay Dissolve about 50 mg of Estriol, accurately weighed, in alcohol to make 100.0 mL, and mix. Dilute 10.0 mL of this solution with alcohol to 100.0 mL. Similarly, dissolve a suitable quantity of USP Estriol RS, accurately weighed, in alcohol to obtain a Standard solution having a known concentration of about 50 µg per mL. Concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 281 nm. Calculate the quantity, in mg, of C18H24O3 in the portion of Estriol taken by the formula:
C(AU / AS)in which C is the concentration, in µg per mL, of USP Estriol RS in the Standard solution, and AU and AS are the absorbances of the solution of Estriol and the Standard solution, respectively.
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