| "In order to investigate the behaviors of transformation of conjugated estrogens (CEs) to free estrogens [FEs; estrone(E1),17βestradiol(E2),estriol(E3)] in wastewater, it is necessary to determine not only FEs but also CEs. Previously, we reported a procedure for determination both of FEs and CEs in wastewater by liquid chromatograph/tandem mass spectrometry (LC/MS/MS). But the recovery ratio of CEs was particularly low for glucuronated estrogens (GEs) less than 30%). In order to overcome, we improved a pretreatment procedure and a subsequent separation by liquid chromatography (LC). This paper explains an improved analytical method for quantifying CEs in wastewater using LC/MS/MS. After addition of an ion-pair reagent and surrogates (E2-3S-d4 and E2-17G-13C4) to the sample, solid phase extraction (SPE) was performed using Oasis HLB cartridge. Subsequently, the cartridge was washed with ethyl acetate/n-hexane solution and eluted with ethyl acetate/methanol solution containing 0.05% ammonia. After solvent removal, the residue was dissolved in acetonitril/water solution, which was then analyzed by LC/MS/MS. (SRM-negative ions with electro splay ionization). the LC-mobil phase used in the gradient mode was acetonitril/water containing 10mmol・L-1 formic acid. For quantification the added surrogates served as internal standards (E2-3S-d4 for SEs and E2-17G-13C4 for GEs, respectively). Applying this method, the method detection limit(MDL) of four sulfated estrogens(SEs) ranged from 0.6 to 1.2ng・L-1 and five GEs ranged from 2.9 to 3.9 ng・L-1. The obtained recovery efficiencies ranged from 80 to 110 % for SEs and 60 to 120 % for GEs, respectively." |
