Determination of Etonogestrel and Ethinyl Estradiol from an Intrauterine Contraceptive Ring by Extraction and Derivative Spectrophotometry
Analytical Letters, 48 (6):
1009-1020 (2015)DOI: 10.1080/00032719.2014.968930
Abstract
A new method for the determination and extraction of ethinyl estradiol and etonogestrel was developed for a pharmaceutical product consisting of a solid copolymer intrauterine ring for subsequent simultaneous quantification by ultraviolet-visible derivative spectrophotometry. The spectral variables were optimized for first derivative spectrophotometry with a smoothing factor of 4000 and an amplification factor of 10,000. A wavelength of 291.5nm was selected for the determination of ethinyl estradiol by a graphical method, while for etonogestrel, zero-crossing was used at 249.5nm. The limits of detection and quantification for ethinyl estradiol were 9.5x10(-7) and 9.0x10(-6)mol/L and 1.1x10(-6) and 3.2x10(-6)mol/L for etonogestrel, respectively. For the extraction method, the variables affecting the analytical signal were the extraction solvent, temperature, and extraction time; optimized conditions were 180min at 76 +/- 2 degrees C in acetonitrile. The method was applied successfully for the first time to analyze intrauterine contraceptive rings. The sample contained 11.7mg etonogestrel and 2.7mg ethinyl estradiol; the recoveries were 93.6 +/- 1.1% etonogestrel and 97.9 +/- 1.5% ethinyl estradiol relative to the nominal concentration. The importance of this method involves its implementation in pharmaceutical laboratories.