Simultaneous Determination of Ethinylestradiol and Levonorgestrel in Oral Contraceptives by Derivative Spectrophotometry

Abstract

A method for determining ethinylestradiol (ETE) and levonorgestrel (LEV) in mixtures by first-derivative spectrophotometry is described. The procedure does not require any separation step. Measurements are made at the zero-crossing wavelengths and the calibration graphs are linear up to 26 and 33 µg ml ^{- 1} of ETE and LEV, respectively. The method was applied to the determination of both compounds in five different Spanish commercial low-dose oral contraceptives. Similar results were obtained by an HPLC method.