Date of Award

Summer 8-21-2015

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

Advisor

Carl P. Tripp

Second Committee Member

Alice E. Bruce

Third Committee Member

Mark Wells

Abstract

The goal of this work was to develop an iron (III) sensor which can be mounted on buoys and gliders and automatically measure iron (III) in the ocean. The method investigated in this thesis was based on anchoring the iron (III) chelator desferrioxamine B (DFB) to magnetic particles. DFB selectively binds iron (III), resulting in a complex which produces a broad absorbance band at 430 nm. This band can be measured via UV-Vis spectroscopy (UV-Vis). However, measuring oceanic iron (III) directly in solution is difficult because the concentrations can be very low, sometimes less than 1 nM. This problem could be solved if one were able to concentrate the iron (III) from a sample and magnetic particles (which can be removed from a solution by introducing a magnet to the side of the container) were used to accomplish this task.

In Chapter 2, it was found that the untreated carbon-coated cobalt magnetic (Co‑C) particles were able to capture iron (III) from a solution. This offered the opportunity to use untreated Co‑C particles to capture iron (III) and then in a second step, remove the iron (III) from the particles for analysis in solution. Most of the studies in Chapter 3 were directed at developing a protocol for extracting iron (III) from the untreated Co‑C particles. In one case, 100% of the iron (III) was removed from the particles with DFB. However, this result was not repeatable – in all other cases, 72% or less of the iron (III) captured from solution was recovered by the DFB. It was determined that this was because the Co‑C particles were exposed to the air between removing the remaining iron solution and adding the DFB. This allowed the iron (III) on the surface to react and form iron oxyhydroxides, meaning that the DFB was not able to capture it all.

In Chapter 4, a variety of magnetic nanoparticles were derivatized with DFB on the surface: Co‑C particles, TurboBeads Silica™ (Co‑C particles purchased with a silica coating), and silica-coated nickel nanoparticles (Ni‑SiO2). It was found that TurboBeads Silica™ treated with DFB or DFB‑Fe (DFB already bound to iron), as well as Ni‑SiO2 treated with DFB-Fe could capture iron (III) from solution. Some of the iron (III) could be removed from the particles by adding oxalate adjusted to a pH of 1.5. However, no more than 70% (usually less) of the iron (III) captured by these particles was ultimately recovered by the oxalate. The DFB on the particles’ surface should have captured the iron (III), preventing it from forming oxyhydroxides. However, to measure iron (III) in the oxalate required adding DFB and adjusting the pH to form the DFB-Fe complex in solution. It was discovered that in a solution of oxalate, DFB-Fe can be reduced to iron (II) when exposed to light. Because measurements were not performed in a dark room, some of the iron (III) was rendered undetectable

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