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Portable monitors for flow injection analysis with potentiometric multiple ion sensors

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Dimitrakopoulos, Telis (1997) Portable monitors for flow injection analysis with potentiometric multiple ion sensors. PhD thesis, University of Tasmania.

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Abstract

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.

Item Type: Thesis (PhD)
Keywords: Electrodes, Ion selective
Copyright Holders: The Author
Copyright Information:

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).

Additional Information:

Thesis (Ph.D)--University of Tasmania, 1998. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:03
Last Modified: 20 Jul 2016 00:13
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