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Metal speciation and characterization of copper complexing ligands in seawater using electrospray ionization mass spectrometry Ross, Andrew R. S.
Abstract
Electrospray ionization mass spectrometry (ESI-MS) provides information regarding the structure and distribution of dissolved polar and ionic metal species which cannot be obtained using electroanalytical or spectroscopic techniques. Such information is necessary if the role of metal complexes in biological and geochemical processes is to be fully understood. The utility of ESI-MS for metal speciation is evaluated using a range of well characterized organic ligands and biogeochemically important metal ions. The technique reveals the stoichiometry and metal oxidation state of organic and inorganic complexes and how speciation changes with solution pH. Results for Cu²⁺ and 8-hydroxyquinoline (HL) show for the first time that ESI-MS can determine the distribution of dissolved metal species at equilibrium. A detection limit of 13 nM for the complex Cu[sup II]L⁺ demonstrates the potential of this technique for studying metal species in natural waters. Ionization of uncharged complexes is achieved by protonation, deprotonation or electrochemical oxidation of the ligand. N,N-Diethyldithiocarbamate oxidation is confirmed by studies involving alkali and alkaline earth metals, which suggest that ESI-MS detection also depends on the polarity and thermodynamic stability of the complex. Metal complexation by large polyfunctional organic compounds is investigated using tannins as model natural ligands. Simultaneous detection of free and complexed tannins allows the effects of metal concentration, pH and ionic strength to be investigated. Determination of ligand structure and copper binding site by tandem mass spectrometry further illustrates the unique capabilities of this technique for metal speciation. ESI-MS is combined with immobilized metal-ion affinity chromatography (IMAC) to extract and characterize copper complexing ligands from British Columbia coastal waters. Initial UV analysis of IMAC extracts suggests that river and surface waters are significant sources of these ligands. Subsequent ESI-MS analysis requires matrix removal which is achieved on-line by flow injection analysis using a custom made XAD- 16 column. A copper ligand of molecular mass 259 is identified in the surface seawater extract with highest UV absorbance. The data are consistent with a dipeptide containing two primary amino groups, a result supported by studies in which IMAC is combined with other methods for characterizing copper ligands in seawater.
Item Metadata
Title |
Metal speciation and characterization of copper complexing ligands in seawater using electrospray ionization mass spectrometry
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1998
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Description |
Electrospray ionization mass spectrometry (ESI-MS) provides information
regarding the structure and distribution of dissolved polar and ionic metal species
which cannot be obtained using electroanalytical or spectroscopic techniques. Such
information is necessary if the role of metal complexes in biological and geochemical
processes is to be fully understood. The utility of ESI-MS for metal speciation is
evaluated using a range of well characterized organic ligands and biogeochemically
important metal ions. The technique reveals the stoichiometry and metal oxidation state
of organic and inorganic complexes and how speciation changes with solution pH.
Results for Cu²⁺ and 8-hydroxyquinoline (HL) show for the first time that ESI-MS can
determine the distribution of dissolved metal species at equilibrium. A detection limit of
13 nM for the complex Cu[sup II]L⁺ demonstrates the potential of this technique for studying
metal species in natural waters. Ionization of uncharged complexes is achieved by
protonation, deprotonation or electrochemical oxidation of the ligand. N,N-Diethyldithiocarbamate
oxidation is confirmed by studies involving alkali and alkaline earth metals,
which suggest that ESI-MS detection also depends on the polarity and thermodynamic
stability of the complex. Metal complexation by large polyfunctional organic compounds
is investigated using tannins as model natural ligands. Simultaneous detection of free
and complexed tannins allows the effects of metal concentration, pH and ionic strength
to be investigated. Determination of ligand structure and copper binding site by tandem
mass spectrometry further illustrates the unique capabilities of this technique for metal
speciation. ESI-MS is combined with immobilized metal-ion affinity chromatography (IMAC)
to extract and characterize copper complexing ligands from British Columbia coastal
waters. Initial UV analysis of IMAC extracts suggests that river and surface waters are
significant sources of these ligands. Subsequent ESI-MS analysis requires matrix
removal which is achieved on-line by flow injection analysis using a custom made XAD-
16 column. A copper ligand of molecular mass 259 is identified in the surface seawater
extract with highest UV absorbance. The data are consistent with a dipeptide
containing two primary amino groups, a result supported by studies in which IMAC is
combined with other methods for characterizing copper ligands in seawater.
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Extent |
8161282 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-05-28
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0061569
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1998-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.