title: Determination of conditional stability constants for some divalent transition metal ion-EDTA complexes by electrospray ionization mass spectrometry.
abstract: Conditional stability constants of coordination complexes comprising divalent transition metals, Cu(2+), Ni(2+), Zn(2+), Co(2+), and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co(2+) and Zn(2+) competed for EDTA at pH 5. When Cu(2+) and Ni(2+) competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered.
authors.affiliation: Fibre Science and Communication Network (FSCN), Mid Sweden University, SE-851 70, Sundsvall, Sweden.
authors.forename: Susanne
authors.initials: S
authors.lastname: Boija
authors.forename: Ann
authors.initials: A
authors.lastname: Almesåker
authors.forename: Erik
authors.initials: E
authors.lastname: Hedenström
authors.forename: Dan
authors.initials: D
authors.lastname: Bylund
authors.forename: Håkan
authors.initials: H
authors.lastname: Edlund
authors.forename: Magnus
authors.initials: M
authors.lastname: Norgren
keywords: EDTA; chelating agent; conditional stability constant; electrospray ionization mass spectrometry; mixed solvent