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Gas‐phase complexes formed between amidoxime ligands and vanadium or iron investigated using electrospray ionization mass spectrometry
Author(s) -
Mustapha Adetayo M.,
Pasilis Sofie P.
Publication year - 2016
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/rcm.7609
Subject(s) - chemistry , vanadium , uranyl , ligand (biochemistry) , electrospray ionization , metal , inorganic chemistry , metal ions in aqueous solution , mass spectrometry , ion , chromatography , organic chemistry , biochemistry , receptor
Rationale Amidoxime‐functionalized sorbents can be used to extract uranium from seawater. Iron(III) and vanadium(V) may compete with uranium for adsorption sites. We use 2,6‐dihydroxyiminopiperidine (DHIP) and N 1 , N 5 ‐dihydroxypentanediimidamide (DHPD) to model amidoxime functional groups and characterize the vanadium(V) and iron(III) complexes with these ligands. We also examine the effect of iron(III) and vanadium(V) on uranyl(VI) complexation by DHIP and DHPD. Methods The experiments were carried out in positive ion mode using a quadrupole ion trap mass spectrometer equipped with an electrospray ionization source. The effect on the mass spectra of changes in ligand, metal:ligand mole ratio, and pH was examined. Results Iron(III) formed a 1:2 metal:ligand complex with DHIP at all metal:ligand mole ratios and pH values investigated; it formed both 1:2 and 1:3 metal:ligand complexes with DHPD. Vanadium(V) formed 1:1 and 1:2 metal:ligand complexes with DHIP. A 1:2 metal:ligand complex was formed with DHPD at all vanadium(V):DHPD mole ratios investigated. Changes in solution pH did not affect the ions observed. The relative binding affinities of the metal ions towards DHIP followed the order iron(III) > vanadium(V) > uranyl(VI). Conclusions This study presents a first look at the gas‐phase vanadium(V)– and iron(III)–DHIP and –DHPD complexes using electrospray ionization mass spectrometry. These metals form stronger complexes with amidoxime ligands than uranyl(VI), and will affect uranyl(VI) adsorption to amidoxime‐based sorbents. Copyright © 2016 John Wiley & Sons, Ltd.