Determination of Etonogestrel and Ethinyl Estradiol from an Intrauterine Contraceptive Ring by Extraction and Derivative Spectrophotometry

• Published in: Analytical letters 2015-04, Vol.48 (6), p.1009-1020
• Main Authors: Toral, M. Inés, Nacaratte, F., Nova, F.
• Format: Article
• Language: English
• Subjects: Contraceptives; Copolymers; Derivatives; Ethinyl estradiol; Etonogestrel; Extraction; Intrauterine contraceptive ring; Mathematical analysis; Pharmaceuticals; Sex hormones; Spectra; Spectrophotometry
• ISSN: 0003-2719; 1532-236X
• DOI: 10.1080/00032719.2014.968930

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 291.5 nm was selected for the determination of ethinyl estradiol by a graphical method, while for etonogestrel, zero-crossing was used at 249.5 nm. The limits of detection and quantification for ethinyl estradiol were 9.5 × 10 −7 and 9.0 × 10 −6  mol/L and 1.1 × 10 −6 and 3.2 × 10 −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 180 min at 76 ± 2°C in acetonitrile. The method was applied successfully for the first time to analyze intrauterine contraceptive rings. The sample contained 11.7 mg etonogestrel and 2.7 mg 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.