Determination of estrogens in river water by gas chromatography–negative-ion chemical-ionization mass spectrometry

A method for the determination of estrogens (17α-estradiol, 17β-estradiol, estrone, ethynyl estradiol, and estriol) as pentafluorobenzyl-trimethylsilyl (PFB–TMS) derivatives by gas chromatography–mass spectrometry (GC–MS) with negative-ion chemical-ionization (NICI) is described. The NICI of all the derivatives produced an intense [M–PFB]− ion as the base peak. The reagent gas (methane) flow-rate and the ion source temperature were determined to be 2.0 ml/min and 240°C, respectively, for the optimized NICI-selected ion monitoring (SIM) conditions. The sensitivities of the PFB–TMS derivatives in the NICI mode were 8.0–130 times higher than those of the PFB–TMS derivatives in electron ionization (EI) mode, and 12–25 times higher than those of all the TMS derivatives in the EI mode. This method was applied to the analysis of estrogens in river water using a solid-phase extraction as the sample preparation. The recoveries of the target chemicals from a river-water sample spiked with standards at 2 ng/l level were 85.8–126.5% (RSD, 6.2–13.0%). The methodical detection limits ranged from 0.10 to 0.28 ng/l.