Fully automated analysis of estrogens in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography–tandem mass spectrometry

Abstract

A simple, rapid and sensitive method for the determination of five estrogens, estrone, 17β-estradiol, estriol, ethynyl estradiol, and diethylstilbestrol, was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC/MS/MS). These estrogens were separated within 8 min by HPLC using an XDB-C8 column and 0.01% ammonia/acetonitrile (60/40, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the negative ion mode were optimized for MS/MS detection of the estrogens. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve ( r ≥ 0.9996) was obtained in the concentration range from 10 to 200 pg/mL for all compounds examined. The limits of detection ( S/ N = 3) of the five estrogens examined ranged from 2.7 to 11.7 pg/mL. The in-tube SPME method showed 34–90-fold higher sensitivity than the direct injection method (5 μL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface water and wastewater samples were collected from the area around Asahi River, and estriol was detected at 35.7 pg/mL in the effluent of a sewage treatment plant. The recoveries of estrogens spiked into river waters were above 86%, except for estriol, and the relative standard deviations were below 0.9–8.8%.