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Fluorometric determination of levonorgestrel and ethinyl estradiol

Khaled M.Elokely, Mohamed A.Eldawy, Mohamed A.Elkersh, Tarek F.El-Moselhy

A simple fluorometric method has been developed, validated and adapted for the quantitative estimation of some drugs that contain methyne groups. This method was based on the formation of a fluorophore as a result of the reaction of active methylene (produced after hydration) containing compounds and N1-methylnicotinamide chloride (NMNCl). The proposed method has been applied successfully to the determination of levonorgestrel (I) and ethinyl estradiol (II) in the pure form, laboratorypreparedmixtures, pharmaceutical dosage forms and in spiked human plasma samples. The method showed linearity over concentration ranging from8-900 pg/ml and 0.5-60 ng/ml, for standard solution of I at pH 11.2 and 4.5, respectively; 5-1,000 pg/ml and 0.5-60 ng/ml, for standard solution of II at pH 12 and 4, respectively. For spiked human plasma samples of I, the linearity covered concentrations ranging from8-900 pg/ml and 0.5-60 ng/ml, at pH 11.2 and 4.5, respectively and for II the linearity covered concentrations ranging from 5-1,000 pg/ml and 0.5-50 ng/ml, at pH 12 and 4, respectively. The method showed good accuracy, specificity and precision in laboratoryprepared mixtures, pharmaceutical dosage forms and spiked human plasma samples. The proposed method is simple, requires no sophisticated instruments and is suitable for quality control application, bioavailability and bioequivalency studies.