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Arsenic Binding to Thiols and Applications to Electrospray Mass Spectrometry Detection Open Access


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Type of item
Degree grantor
University of Alberta
Author or creator
McKnight-Whitford, Anthony Nicholai
Supervisor and department
Le, X.Chris (Analytical and Environmental Toxicology)
Examining committee member and department
Lucy, Charles (Chemistry)
Dasgupta, Sandy (Chemistry and Biochemistry-University of Texas)
Harynuk, James (Chemistry)
St. Louis, Vincent (Biological Sciences)
Campbell, Robert (Chemistry)
Department of Chemistry

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Arsenic is a widespread environmental contaminant whose toxicity depends on its valence and its chemical form. Arsenic species have been typically determined using high pressure liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICPMS), however ICPMS cannot differentiate the co-eluting arsenic species. This thesis explores the use of electrospray mass spectrometry (ESI-MS) with HPLC separation for arsenic speciation and demonstrates applications of various HPLC-ESI-MS methods for the determination of toxicologically and environmentally relevant arsenic compounds. The trivalent arsenicals, such as arsenite (AsIII) and its metabolites monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) are not easily detected using ESI-MS due to their poor ionizability, but they are known to have high affinity for thiols. Thus, the easily ionizable dithiol dimercaptosuccinic acid (DMSA) was used to derivatize the trivalent arsenicals prior to ESI-MS. Selection of the derivatizing reaction was based on studies of arsenic-thiol interactions. An HPLC-ESI-MS/MS method was developed for the detection of derivatized AsIII, DMAIII and MMAIII and underivatized arsenate (AsV), monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV), and was used to analyze multiple types of samples including urine, plasma and water. One set of groundwater samples from the site of a former pesticide manufacturing plant contained concentrations of MMAIII as high as 3.9-274 mg/L, the highest ever observed in the environment. Another HPLC-ESI-MS/MS method, without the need of derivatization, was developed for the detection of the toxic thio-arsenicals dimethylmonothioarsinic acid (DMMTAV) and monomethylmonothioarsonic acid (MMMTAV). DMMTAV was present in rat plasma and human urine and both DMMTAV and MMMTAV were detected in rat urine. The method of derivatization and ESI-MS/MS detection was extended to the speciation of inorganic SbIII and SbV. The use of the HPLC-ESI-MS/MS method using DMPS derivatization enabled the speciation of SbIII and SbV in water samples from mine waste.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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