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Title: Arsenic speciation analysis in food-related and environmental samples
Author: Taebunpakul, Sutthinun
ISNI:       0000 0004 2699 1383
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2011
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Metallomics approaches based on the combined use of elemental and molecular mass spectrometry for arsenic speciation analysis in phytoremediating plants, marine algae, cut tobacco and cigarette smoke total particulate matter have been developed. Size-exclusion chromatography (SEC)-ICP-MS is proposed to use as a powerful tool for selecting both the appropriate extractant as well as optimum extraction conditions. Comparative SEC-ICP-MS As profiles and total As concentrations in the extracts were used to identify the optimum condition for As speciation studies as a compromise between extraction efficiency and preservation of compound identity. Methodologies have been developed to gain a better grasp of the factors involved in the uptake and distribution of As in the hydroponically grown Arabidopsis thaliana. The effect of the presence of Se on the As and Hg incorporated into the leaves was investigated here for the first time; Se in the growing media was found not to affect As and Hg concentrations in the leaves. Results also revealed the presence of small amounts of As-PC3, As-PC4 and As-PC5 complexes in the leaves, which were characterized by ESI-Orbitrap MS to minimize ambiguity in species identification. The application of an in vitro dialysis method for predicting the As bioaccessibility in selected edible marine algae, was investigated here for the first time. Results showed low As dialyzability (10-20%) and no transformation of As species, primarily arsenosugars, observed following in vitro gastrointestinal digestion. Knowledge of the distribution of arsenic species in cut tobacco, obtained by sequential extraction, provides an insight into the transformation of arsenic species during the combustion process when the cigarette is burnt. The combustion of organic compounds present in tobacco resulted in the change of redox state and As-species distribution in tobacco smoke. Both the hyphenated MS and XANES techniques were used to obtain information about arsenic speciation in smoke condensates. The results showed that the tobacco smoke contained a mixture of As(III) and As(V); As(III) being found as arsenite and, possibly, thio-arsenite by HPLC-ICP-MS. The reduction of As(V) to As(III) during dynamic cigarette smoke formation can be explained by the overall smoke redox properties in accordance with the cigarette combustion process.
Supervisor: Jarvis, Kym ; Parry, Susan ; Lee, Bill Sponsor: Thai Ministry of Science and Technology ; British American Tobacco
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral