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 micrograms 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.
A micellar electrokinetic chromatograpliic method which permits the separation of very similar compounds such as ethinylestradiol (ETE), gestodene (GTD), (-)norgestrel (LEV) and p-estradiol valerate (EST) from synthetic mixtures is described. The study was carried out at 25°C and 20 kV, using a 15 mM borate •Tel. 2454 BERZAS, CASTANEDA, AND PINILLA buffer (pH 9.2), 15 mM sodium dodecylsulfate (SDS) and 26 % acetonitrile-water as background electrolyte. The analysis takes about 12 minutes.
A capillary gas chromatographic method with flame ionisation detection (FID) has been developed for the analysis of Tamoxifen, Anastrozole, and Letrozole in their pharmaceutical preparations, using Clomipramine as the internal standard in order to achieve quantification. Optimal conditions were investigated: column head pressure (110 kPa), injector and detector (FID) temperatures (both 3258C), time and temperature for the splitless step (0.75 min and 708C), volume injected (2 lL), and an oven temperature program providing analysis times shorter than 8 minutes. The principal aspects of the validation method are examined and discussed. A test of the ruggedness of this method was carried out using the Plackett-Burman fractional factorial model with a matrix of fifteen experiments. Detection limits of 17.0, 9.6, and 30.6 lg L -1 were obtained for Tamoxifen, Anastrozole, and Letrozole, respectively. This method is simple, rapid, and sensitive; it was tested on the analysis of pharmaceutical preparations, achieving recoveries between 98.8% and 100.3%.
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