Nanostructured solvent based microextraction followed by a novel strategy for online phase separation coupled with HPLC for determination of ethinyl estradiol

Abstract

Supramolecular solvent microextraction coupled with high performance liquid chromatography based on a new strategy for phase separation was developed for determination of ethinyl estradiol in water samples. Ethinyl estradiol was extracted from 10 mL of a water sample into a supramolecular solvent, a nanostructured solvent, which was formed in situ from reverse micelles of a biosurfactant in a THF–water solution. After extraction, the supramolecular solvent was retained in an inline filter and was separated from the aqueous solution and then, it was eluted and transferred to an HPLC column. Experimental design and response surface methodology (RSM) were used for optimization of different parameters that influence the extraction efficiency of the method. Under optimal conditions, ethinyl estradiol was effectively extracted and a preconcentration factor of 237 was obtained. The calibration curve was investigated in the concentration range of 0.1–200 μg L⁻¹ and good linearity was achieved with a coefficient of determination better than 0.995. A detection limit of 0.1 μg L⁻¹ and suitable precision with RSD = 5.1% (n = 3) were obtained. Finally, the proposed method was applied to determine the concentrations of ethinyl estradiol in different water samples and provided acceptable recoveries.