Evaluation of the micro liquid|liquid interface towards electroanalytical detection of Fe²⁺ and trace metal ions in terrestrial and seawater

Jiang, Qi (2021) Evaluation of the micro liquid|liquid interface towards electroanalytical detection of Fe²⁺ and trace metal ions in terrestrial and seawater. Masters thesis, Memorial University of Newfoundland.

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Abstract

As the primary production of phytoplankton is the foundation of the global carbon cycle, monitoring the spatiotemporal concentration of iron, which is a key micronutrient often limiting the growth of phytoplankton in the ocean, has been a focus in oceanic and terrestrial waters for several decades. Herein, we propose to evaluate a novel method of iron detection at a micro interface between water|1,2-dichloroethane (w|DCE) and water|ionic liquid (w|IL). Ligand assisted charge transfer of Fe²⁺ was monitored electrochemically using cyclic and differential pulse voltammetry (CV and DPV). Chapter 1 introduces some techniques used for detection of iron in the seawater and contemporary analytical methods in the field, as well as fundamental concepts of electrochemistry at the interface between two immiscible electrolyte solutions (ITIES), so-called liquid|liquid electrochemistry. Chapter 2 describes the main body of work in which four ligands were investigated toward facilitated Fe²⁺ transfer, including 1,10-phenathroline (phen), 1-nitroso-2-naphthol (N2N), 2-(2-thiazolylazo)-p-cresol (TAC), and salicylaldoxime (SAL). The overall complexation or binding constant for each ion was determined and compared versus Fe2+ coordination at the w|DCE micro-interface. Three Fe²⁺:phen, metal:ligand, stoichiometries were observed; however, only a single stoichiometry was recorded in the case of the other ligands. Chapter 3 describes a preliminary investigation of facilitated Fe²⁺ transfer reactions using phen at a water|ionic liquid (w|IL) interface, while Chapter 4 provides some overall conclusions and perspectives as to the direction of the field moving forward.

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