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Development and characterisation of a colorimetric binding phase for the diffuse gradients in thin films technique

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McGifford, Russell William (2011) Development and characterisation of a colorimetric binding phase for the diffuse gradients in thin films technique. PhD thesis, University of Tasmania.

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Abstract

Passive sampling is a useful method for contaminant analysis and monitoring, and of
the techniques available the Diffusive Gradients in Thin Films (DGT) technique is
particularly applicable for use in transition metal studies. However, analysis of the
metal-accumulating DGT 'binding phase' is typically expensive and time
consuming, which limits the technique's application. In order to improve on the cost
and speed of analysis, and to allow in-field analysis, a colorimetric binding phase
was developed. By employing metallochromic reagents adsorbed onto ion-exchange
resins a colour change was obtained as a result of the binding of metal ions, with the
degree of change being proportional to the quantity of complexed metal. This
reagent-adsorbed resin was immobilised on adhesive paper labels to provide a
robust, cheap and effective colorimetric binding phase.
Quantification of metal loading on these binding phases was undertaken through use
of UV-Vis reflectance or Computer Imaging Densitometry (CID), the latter
employing a flat-bed scanner for improved ease of analysis. Analytically robust
metal quantification was found to be achievable using these methods, with the CID
method equivalent in performance to the reflectance method. The use of a variety of
metallochromic reagents was explored, with different reagents noted to provide
colorimetric responses for different metal ions.
A typical detection limit, provided by Methylthymol Blue adsorbed to Dowex 1x8
resin, was 10 ng Cu(II) per cm-2 of disc area. Linear response was seen up to a
stoichiometrically defined metal loading, typically providing a linear response from
the detection limit to 2 µg of Cu(II) per cm-2. Selectivity was reagent dependant, in
particular Zincon was seen to provide a selective response to Cu(II) at neutral pHs
and is a promising candidate for deployment of these colorimetric DGT binding
phases.

Item Type: Thesis (PhD)
Copyright Holders: The Author
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Copyright 2011 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
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Available for use in the Library and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2011. Includes bibliographical references

Date Deposited: 19 Dec 2014 02:56
Last Modified: 25 Sep 2017 07:56
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