title: Bio-uptake of metalloids (inorganic antimony and arsenic) by plants and development of electroanalytical methods for antimony detection and speciation
Creators: name: Tuyogon, Dennis
Publisher: name: University of Liverpool Repository
Year: 2021

description: Metalloids like arsenic (As) and antimony (Sb) are naturally present at low concentrations but the increased use of these metalloids in the environment has led to environmental soil and groundwater contamination issues and understanding their biogeochemical cycling is of prime importance to predict potential contamination issues. Despite its toxicity, Sb received little analytical attention compared to other toxic heavy metals. However, speciation analysis is necessary to understand the toxicity and fate of each metalloid species in the environment. The speciation of metalloids is however often limited to the differentiation of oxidation states and identification of stable organic species by techniques such as ICP and LC-MS. The detection and identification of more reactive, relatively weak complexes that can play a preponderant role in the transport of these elements are however much less known. There is a wide range of available spectroscopic techniques for total Sb and As determination and speciation in real environmental samples. But the equipment often used for such analysis is bulky, expensive, and immobile. The necessity for a cheap, portable, smaller, and simpler analytical technique that can be used in the field were all the reasons for using electrochemical methods. One of the techniques is by using a gold microwire electrode that is well suited for the speciation of inorganic arsenic and antimony that has the advantage of low cost, portability, and may detect weak complex. The main focus of this study is trying to understand where metalloid species are ending up and how they are being transported. This thesis investigated the bio-uptake of metalloids (inorganic antimony and arsenic) by plants and the development of electroanalytical methods for antimony detection and speciation. Bio-uptake of metalloids were using a hydroponic experiment of cucumber plant chosen as a model plant to assess the impact of As or Sb species, plant age, exposure duration, and metalloid concentration to overall plant morphology. A new method of microdialysis was developed. Being less destructive and less invasive, it can be a useful tool for xylem sap sampling allowing researchers to simulate nutrient/toxic metal uptake, translocation, and absorption while taking into consideration the effect of transpiration. The other aim of this study is to use voltammetry to study the complexation of such elements with e.g. carboxylic acids, preponderant components of xylem sap that might strongly affect the translocation of As and Sb. Voltammetric methods were developed for (1) complexation studies of Sb(III) with xylem sap samples and determination of stability constants of Sb(III) with low molecular weight ligands and cation mediated reduction of Sb(V) using monovalent, divalent, and trivalent cations. We have demonstrated the feasibility to quantitatively study the complexation of the presence of Sb(III) complex with low molecular weight ligands, specifically EDTA, DTPA, TA, and GSH using a voltammetric method (pseudopolarography on Au electrode) at ppb levels. The technique may also be that will be used to gain insights into the complexation patterns of inorganic and organic bound Sb and highlight the formation of weak, fast dissociating species as well as inert, stable, complexes. Voltammetry may complement nicely the commonly that will be used chromatographic and hyphenated techniques.