SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF ETHINYLESTRADIOL ANDLEVONORGESTREL BY PARTIAL LEAST-SQUARES AND PRINCIPAL COMPONENT REGRESSION MULTIVARIATE CALIBRATION

Two spectrophotometric methods for the determination of Ethinylestradi ol (ETE) and Levonorgestrel (LEV) by using the multivariate calibratio n technique of partial least square (PLS) and principal component regr ession (PCR) are presented. In this study the PLS and PCR are successf ully applied to quantify both hormones using the information contained in the absorption spectra of appropriate solutions. In order to do th is, a calibration set of standard samples composed of different mixtur es of both compounds has been designed. The results found by applicati on of the PLS and PCR methods to the simultaneous determination of mix tures, containing 4-11 mu g ml(-1) of ETE and 2-23 mu g ml(-1) of LEV, are reported. Five different oral contraceptives were analyzed and th e results were very similar to that obtained by a reference liquid chr omatographic method.