Estrogenic compounds determination in water samples by dispersive liquid-liquid microextraction and micellar electrokinetic chromatography coupled to mass spectrometry

In this work, a group of 12 estrogenic compounds, i.e., four natural sexual hormones (estrone, 17 beta-estradiol, 17 alpha-estradiol and estriol), an exoestrogen (17 alpha-ethynylestradiol), a synthetic stilbene (dienestrol), a mycotoxin (zearalenone) and some of their major metabolites (2-methoxyestradiol, alpha-zearalanol, beta-zearalanol, alpha-zearalenol and beta-zearalenol) have been separated and determined by micellar electrokinetic chromatography (MEKC) coupled to electrospray ion trap mass spectrometry. For this purpose, a background electrolyte containing an aqueous solution of 45 mM of perfluorooctanoic acid (PFOA) adjusted to pH 9.0 with an ammonia solution, as MS friendly surfactant, and methanol (10% (v/v)), as organic modifier, was used. To further increase the sensitivity, normal stacking mode was applied by injecting the sample dissolved in an aqueous solution of 11.5 mM of ammonium PFO (APFO) at pH 9.0 containing 10% (v/v) of methanol for 25 s. Dispersive liquid-liquid microextraction, using 110 mu L of chloroform and 500 mu L, of acetonitrile as extraction and dispersion solvents, respectively, was employed to extract and preconcentrate the target analytes from different types of environmental water samples (mineral, run-off and wastewater) containing 30% (w/v) NaCl and adjusted to pH 3.0 with 1 M HCl. The limits of detection achieved were in the range 0.04-1.10 mu g/L. The whole method was validated in terms of linearity, precision, recovery and matrix effect for each type of water, showing determination coefficients higher than 0.992 for matrix-matched calibration and absolute recoveries in the range 43-91%. (C) 2014 Elsevier B.V. All rights reserved.