Determination of estrogens in environmental water samples by LC/MS/MS

An analytical method for the simultaneous determination of estrogens (17bet a-estradiol, 17alpha-estradiol, estrone, ethinylestradiol) by liquid chroma tography/tandem mass spectrometry (LC/MS/MS), following sample pretreatment by solid-phase extraction using a C-18 cartridge, back extraction from the water phase with ethyl acetate and cleaned up using NH2 cartridge, has bee n developed. It has been observed that the main fragment negative ions with electrosplay ionization (ESI) were deprotonated molecules, [M - H](-), for each compound, as follows: 17beta-estradiol and 17alpha-estradiol, m/z 271 ; estrone, m/z 269; ethinylestradiol, m/z 295. The product ion, m/z 145, wa s obtained from all compounds using a collision energy of 50 eV. The detect ion limits of four compounds ranged from 0.1 ng/ml to 0.5 ng/ml. Good linea rity (r greater than or equal to 0.998) of the calibration curve was obtain ed in the concentration range from 0.5 ng/ml to 100 ng/ml for all compounds . The present method has been successfully applied to the determination of estrogens in environmental water samples, such as river water and the disch arge of sewage treatment plants.