Comparison of electrospray ionization, atmospheric pressure chemical ionization and atmospheric pressure photoionization for determining estrogenic chemicals in water by liquid chromatography tandem mass spectrometry with chemical derivatizations

Abstract

This study compared the sensitivities and matrix effects of four ionization modes and four reversed-phase liquid chromatographic (LC) systems on analyzing estrone (E1), 17beta-estradiol (E2), estriol (E3), 17alpha-ethinylestradiol (EE2), 4-nonylphenol (NP), 4-tert-octylphenol (OP), bisphenol A (BPA) and their derivatives of dansyl chloride or pentafluorobenzyl bromide (PFBBr) in water matrixes using a triple-quadrupole mass spectrometer with selected reaction monitoring (SRM). The four probes were electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI) and APCI/APPI; the four LC systems were ultra-performance liquid chromatography (UPLC) with or without post-column split, a mixed-mode column and two-dimensional LC (2D-LC). Dansylated compounds with ESI at UPLC condition had the most intense signals and less matrix effects of the various combinations of ionization and LC systems. The on-column limits of detection (LODs) of dansylated estrogens by SRM were 0.05-0.20 pg, and the LODs in sewage treatment plant effluent and in river water were 0.23-0.52 and 0.56-0.91 ng/L, respectively. The LODs using selected ion monitoring (SIM) reached low ng/L levels in real samples and measured concentrations were comparable with those of SRM.