Determination of estrogens in dosage forms by fluorescence using dansyl chloride

A sensitive, reproducible, fluorometric procedure for the determination of estrogens in pharmaceutical preparations is presented. The estrogens are determined fluorometrically following their reaction with dansyl chloride. The optimum conditions for the reaction such as pH, reaction solvent composition variations, and speed of reaction are discussed. In addition, a linearity study of the relationship between concentration and fluorescence intensity for estrone, estradiol, and ethinyl estradiol is reported. Solvent extraction procedures based on acid-base behavior or column chromatography are used when necessary to isolate the estrogen prior to reaction with dansyl chloride and fluorometric measurement. The recovery of estrogens from spiked samples indicated that the proposed method is efficient and reproducible. Comparison of the dansyl procedure with the official NF method in the analysis of estrone aqueous suspension showed the proposed method to be accurate and more precise than the NF assay. Estrone aqueous suspension, estradiol in sesame oil, estradiol valerate in castor oil and in sesame oil (in the latter case, in the presence of testosterone), estradiol benzoate in sesame oil, and ethinyl estradiol tablets (0.5 mg/tablet) from commercial sources were satisfactorily analyzed, with average results within compendial limits and no coefficient of variation greater than 2%.