Kabagambe, Benjamin
(2016)
ELECTROCHEMICAL ION-IONOPHORE RECOGNITION AT MEMBRANE/WATER INTERFACES FOR ULTRATRACE ION SENSING.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
ELECTROCHEMICAL ION-IONOPHORE RECOGNITION AT MEMBRANE/WATER INTERFACES FOR ULTRATRACE ION SENSING
Benjamin Kabagambe, PhD
University of Pittsburgh, 2015
Electrochemical methods for trace ion analysis of organic and inorganic species with environmental and biological attention have been developed and reported during past decades. Voltammetric method is attractive not only to analyze selective ion species due to its characteristic based on ion lipophilicity, but also to lower the limit of detection by combining with stripping analysis. In my PhD work, I have developed a highly selective and sensitive electrochemical ion-ionophore recognition method that can be used to characterize fundamental transport dynamics at membrane/water interfaces. I have also demonstrated that my selective and sensitive electrochemical technique is useful for very low detection of trace ions. Specifically, cyclic voltammograms of Ag+, K+, Ca2+, Ba2+, and Pb2+ transfers facilitated by highly selective ionophores are measured and analyzed numerically using the E mechanism to obtain standard IT rate constants in the range of 0.01–0.001 cm/s at plasticized poly(vinyl chloride) membrane/water. We utilized ultrathin polymer membrane to maximize a current response by complete exhaustion of preconcentrated ions to detect nanomolar potassium ions using K+-selective valinomycin doped membrane. The selectivity of this membrane further reveals presence of NH4+ -valinomycin complex which is 60 times less stable than K+-valinomycin complex. This work also becomes the first to reveal 5nM K+ contamination of lab nanopure water hence the need for cleaner ultrapure water to achieve a 0.6nM K+ LOD. We further quantitatively confirm the charge-dependent sensitivity theory by stripping voltammetry experiments of divalent ion i.e. Ca2+. Specifically, the achievement of the subnanomolar LOD required two advantageous effects of higher analyte charge on sensitivity in addition to the careful prevention of the Ca2+ contamination of background solutions. Furthermore, we use the ionophore free double-polymer modified electrode to study lipophilicity of perfluoroalkyl surfactants. Advantageously, the high lipophilicity of perfluorooctane sulfonate allows for its stripping voltammetric detection at 50 pM in the presence of 1 mM aqueous supporting electrolytes, a ~10^7 times higher concentration. Significantly, this detection limit for perfluorooctane sulfonate is unprecedentedly low for electrochemical sensors and is lower than its minimum reporting level in drinking water set by the US Environmental Protection Agency.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
| Creators | Email | Pitt Username | ORCID  |
|---|
| Kabagambe, Benjamin | bek44@pitt.edu | BEK44 | |
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| ETD Committee: |
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| Date: |
19 January 2016 |
| Date Type: |
Publication |
| Defense Date: |
24 November 2015 |
| Approval Date: |
19 January 2016 |
| Submission Date: |
1 December 2015 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
192 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Electrochemical Sensors, Ion-Ionophore Recognition, Stripping Voltammetry, Ultratrace |
| Date Deposited: |
19 Jan 2016 21:38 |
| Last Modified: |
15 Nov 2016 14:30 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/26190 |
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