title: Determination of dissolved metal species by electrospray ionization mass spectrometry.
abstract: The distribution of metal species in solution was determined using flow injection electrospray ionization mass spectrometry. Complexes formed by selected metal ions with added organic ligands in 50:50 water/acetonitrile and 50:50 water/methanol under acidic, neutral, and basic conditions were detected using electrospray ionization conditions optimized to best represent solution-phase interactions. Metal species containing acetate, nitrate, and solvent molecules predominated in acidic solution but became less abundant at higher pH. Interactions between metal ions and added organic ligands became more selective with increasing pH, showing the expected preference of hard and soft ligands for metal ions of the corresponding type. Species distributions also tended toward larger complexes as pH increased. Overall ion yield was greater for aqueous acetonitrile than for aqueous methanol solutions; however, reduction of copper(II) in aqueous acetonitrile resulted in the detection of copper(I) complexes for certain ligands. Experimental results for copper(II) and 8-hydroxyquinoline in 50:50 water/methanol showed good agreement with aqueous speciation predicted using the thermodynamic equilibrium model MINEQL. Detection of neutral complexes was achieved by protonation, deprotonation, or electrochemical oxidation during electrospray.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1, and Contaminants Science Section, Institute of Ocean Sciences, 9860 West Saanich Road, Sidney, British Columbia, Canada V8L 4B2.
authors.forename: A R
authors.initials: AR
authors.lastname: Ross
authors.forename: M G
authors.initials: MG
authors.lastname: Ikonomou
authors.forename: J A
authors.initials: JA
authors.lastname: Thompson
authors.forename: K J
authors.initials: KJ
authors.lastname: Orians