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Ratiometric analysis of the ferrocene boronate esters of 2‐ and 4‐hydroxyestradiol by tandem electrospray mass spectrometry
Author(s) -
Williams Dudley,
Chen Shiuan,
Young Mary K.
Publication year - 2001
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/1097-0231(20010215)15:3<182::aid-rcm208>3.0.co;2-o
Subject(s) - chemistry , electrospray ionization , tandem mass spectrometry , electrospray , mass spectrometry , ferrocene , ion trap , extractive electrospray ionization , catechol , chromatography , selected reaction monitoring , organic chemistry , electrode , electrochemistry
A method has been developed for the semiquantitative analysis of the catechol estrogens, 2‐ and 4‐hydroxyestradiol, using tandem electrospray mass spectrometry in a quadrupole ion trap mass analyzer. The implication of catechol estrogens in the biogenesis of breast and prostate cancer makes these labile lipophilic compounds important analytical targets. Ferrocene boronic acid is reacted with 2‐ and 4‐hydroxyestradiol to form their cyclic boronate esters. Sample ionization is accomplished during the electrospray process by a one‐electron oxidation of the ferrocene functionality to form the radical cation. The analysis depends on a non‐aqueous solvent system consisting of 90% acetonitrile and 10% dichloromethane with 100 µM lithium triflate as the supporting electrolyte. The sensitivity of the analysis is greatly increased by the use of a novel electrospray interface with a large surface area stainless steel electrode coupled to a pulled fused‐silica needle. Collision‐induced dissociation of the selected molecular ion within the ion trap produces fragment ion spectra that can be used to distinguish between the two isobaric isomers and ultimately determine the relative amounts in mixtures containing both components. The method is sensitive to analyte concentrations in the low nM range. Copyright © 2001 John Wiley & Sons, Ltd.