Formation of multiple trimethylsilyl derivatives in the derivatization of 17alpha-ethinylestradiol with BSTFA or MSTFA followed by gas chromatography-mass spectrometry determination.

Sate Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Journal of Environmental Sciences (Impact Factor: 1.92). 02/2007; 19(7):879-84. DOI: 10.1016/S1001-0742(07)60146-6
Source: PubMed

ABSTRACT N,O-bis(trimethylsily)trifluoroacetamide (BSTFA) and N-methyl-N(trimethylsily) trifluoroacetamide (MSTFA) are common derivatization reagents used in the GC-MS analysis of estrogen steroids such as estrone (El) and 17alpha-ethinylestradiol (EE2). In this study, three trimethylsilyl (TMS) steroid derivatives, mono- and di-trimethylsilyl EE2 and mono-trimethylsilyl E1, were observed during the derivatization of EE2 with BSTFA or MSTFA and/or GC separation. Factors influencing the production of multiple TMS derivatives and their relative abundance were examined. It was found that both methanol and bisphenol A competed with estrogenic esteroids when reacting with silylation reagents, and thus affected the formation of TMS derivatives and their relative abundance in the derivatization products. Methanol was found to be more reactive than bisphenol A with the BSTFA reagent. None of the three solvents tested in this study could prevent the generation of multiple TMS derivatives during the derivatization of EE2 with BSTFA, followed by GC analysis. A similar result was observed using MSTFA as the derivative reagent followed by GC analysis. Thus, the suitability of BSTFA or MSTFA as the derivatization reagent for the determination of E1 and EE2 by GC-MS, under the conditions reported here, is questionable. This problem can be solved by adding trimethylsilylimidaz (TMSI) in the BSTFA reagent as recommended, and the performance of the method has been proved in this study.

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    ABSTRACT: Comprehensive two-dimensional gas chromatography (GC × GC) hyphenated with rapid quadrupole mass spectrometry was successfully used to develop a novel method for the determination of trace level estrogens in influent and effluent wastewater. Five estrogens used for the study were 17β-estradiol (βE2), 17α-estradiol (αE2), estrone (E1), 17α-ethynylestradiol (EE2) and estriol (E3). Two orthogonal columns and thermal modulation result in enhanced separation, while the rapid scanning quadrupole mass spectrometer gives high resolution peaks. Samples were extracted with Hydrophilic–Lipophilic Balance (HLB) cartridges and derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) prior to analysis. The method uses a single extraction step and ng L−1 method detection limits were achieved using a relatively low sample volume of 500 mL. Elimination of additional cleanup steps make the method time effective. Furthermore, the method has less initial cost as the instrument is far less expensive than a tandem mass spectrometer. A parallel conventional gas chromatographic-mass spectrometric (GC/MS) study was carried out to compare the results. Detection limits were 2 to 4 times improved with the GC × GC over the GC/MS.
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