University of Tasmania
whole_DimitrakopoulosTelis1998_thesis.pdf (21.9 MB)

Portable monitors for flow injection analysis with potentiometric multiple ion sensors

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posted on 2023-05-27, 00:15 authored by Dimitrakopoulos, Telis
The use of multi-sensing portable monitors is of increasing importance for many applications in modern technology. This thesis reports on the development of a new portable battery-powered flow injection potentiometric (FIP) system suitable for remote-site monitoring that can utilise a range of ion-selective electrodes (ISEs) or arrays of coated-wire electrodes (CWEs) as detectors. A number of different designs were developed and evaluated for a variety of applications. Portable FIP systems employing: (1) a commercial iodide ISE as a single electrode detector, and (2) a tungsten / tungsten-oxide wire electrode employed as a pH sensor were initially developed. The performance of the iodide electrode exhibited near-Nernstian response over a wide concentration range in the FIP mode. The tungsten / tungsten-oxide electrode exhibited a subNernstian response between the pH range 2 and 11, and was used to determine the pH of various samples in the FIP mode. Three commercial planar type ISEs (nitrate, potassium and sodium) were arranged in a three-ISE array and used in the portable FIP system. The potassium and sodium ISEs exhibited Nernstian responses, while the nitrate ISE exhibited a near-Nernstian response. The accuracy of the ISE-array was studied and validation of this system was performed with various mineral water samples in the FIP mode. An eight electrode flow-through cell was developed in a portable HP system and evaluated in the FIP mode with metallic silver electrodes. These were each anodised with iodide and the responses of the individual electrodes to silver and iodide standard solutions were studied. Individual photo-cured bisphenol A epoxydiacrylate membrane based CWEs for ammonium, calcium, hydrogen, nitrate and potassium were developed and evaluated using silver wire electrodes in the eight-electrode flow cell described above. Each photo-cured CWE exhibited Nernstian response over a wide concentration range in the steady-state mode and was selective and fast responding taking <5 seconds to attain 90% of the steady-state value, making them ideal for a multi-CWE arrangement in FIP. These photo-cured CWEs were successfully used to determine the respective ions in various water samples. Three multi-CWE arrangements employing the photo-cured membranes mentioned above have been investigated in the FIP mode; namely (1) a two sensor array consisting of ammonium and hydrogen CWEs; (2) a four sensor array consisting of calcium, nitrate, potassium CWEs and a Ag/AgC1 wire electrode; and (3) a six sensor array consisting of ammonium, calcium, hydrogen, nitrate and potassium CWEs and a Ag/AgC1 wire electrode. The multi-CWE arrangements were used to measure the respective ions simultaneously in various water samples in the PIP mode.


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Copyright 1997 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s). Thesis (Ph.D)--University of Tasmania, 1998. Includes bibliographical references

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