Trace analysis of diethylstilbestrol, dienestrol and hexestrol in environmental water by Nylon 6 nanofibers mat-based solid-phase extraction coupled with liquid chromatography-mass spectrometry

Abstract

A simple, rapid and sensitive method for the determination of diethylstilbestrol (DES), dienestrol (DE) and hexestrol (HEX) was developed by using the Nylon 6 nanofibers mat-based solid-phase extraction (SPE) coupled with liquid chromatography–tandem mass spectrometry (LC–MS). These estrogens were separated within 8 min by LC using an ODS column and methanol/water (80/20, v/v) at a flow rate of 1.0 mL min⁻¹. Electrospray ionization conditions in the negative ion mode were optimized for MS detection of the estrogens. Under the optimum SPE conditions, all target analytes in 50 mL environmental water samples can be completely extracted by 1.5 mg Nylon 6 nanofibers mat at flow rate of 3.0 mL min⁻¹ and easily eluted by passage of 500 μL mobile phase. By using the novel SPE-LC/MS method, good linearity of the calibration curve (r² ≥ 0.9992) was obtained in the concentration range from 0.10 ng L⁻¹ to 1.0 mg L⁻¹ (except for DE which was 0.20 ng L⁻¹ to 1.0 mg L⁻¹) for all analytes examined. The limits of detection (S/N = 3) of the three estrogens ranged from 0.05 ng L⁻¹ to 0.10 ng L⁻¹. This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several water samples were collected from Jinchuan River and Xuanwu Lake, and in Jinchuan River water DES was detected at 0.13 ng L⁻¹. The recoveries of estrogens spiked into tap water were above 98.2%, and the relative standard deviations were below 4.78%.