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Capillary electrochromatography of inorganic and small organic anions using pseudo and wall-coated ion exchange phases

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Breadmore, MC (2001) Capillary electrochromatography of inorganic and small organic anions using pseudo and wall-coated ion exchange phases. PhD thesis, University of Tasmania.

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Abstract

This work presents a systematic study on the use of pseudo-phase and wall-coated
ion-exchange (IE) phases for the separation of anions by ion-exchange capillary
electrochromatography (IE-CEC).
The viability of using open tubular (OT) columns prepared by adsorbing small
cationic particles onto the capillary wall for the selectivity manipulation of inorganic
anions by IE-CEC was examined. The introduction of an IE component into the
separation mechanism allowed the separation selectivity to be varied by changing
the type and concentration of the electrolyte anion. This enabled the migration order
of a mixture of ions to be changed from a chromatographic selectivity to an
electrophoretic selectivity, via novel intermediate selectivities. When separating UV
transparent ions, the IE competing ion also acted as the indirect detection probe,
which restricted the range over which the concentration could be varied. Selectivity
manipulation in this case was achieved by varying the type of probe rather than its
concentration. Using a theoretical model equation derived from IC and CE theory,
the manner in which mobilities changed with varying electrolyte composition was
modelled, with excellent correlation being obtained between predicted and
experimental analyte mobilities (r2> 0.98). Values for analyte constants determined
from non-linear regression allowed a quantitative comparison of the strengths of
interaction of different ions with the ion-exchange phase.
The addition of the cationic polymer, poly(diallyldimethylammonium chloride), to
the electrolyte as an alternative to OT columns provided superior flexibility due to
the ability to vary the IE capacity. The model derived for the migration of anions in
the OT system was extended to include the ability to vary the IE capacity and was
validated with a test set of 16 UV absorbing inorganic and organic anions. Excellent
agreement (r2> 0.98) was obtained between experimental and predicted mobilities
for all ions. The model was used to find the optimum separation conditions, with
the separation of 16 ions being achieved on the basis of only 5 initial experiments.
The system was then extended to the analysis of UV transparent ions where the
separation of 24 anions was optimised using the derived model equation. The
potential of using pseudo-phase IE-CEC for the separation of real samples was
demonstrated with the separation of anions in Bayer liquor.
The advantage of having a heterogeneous phase in an OT column was exploited to
enable the on-capillary preconcentration of inorganic anions via IE interactions. A
new elution method, namely the use of a transient isotachophoretic gradient, was
introduced and shown to be a very efficient method for analyte elution from the
preconcentration column. A fundamental study of the generation and
implementation of the gradient was undertaken and the optimum conditions enabled
nearly a 1000-fold increase in sensitivity over conventional CE without the use of
electrokinetic injection. The potential of the method was demonstrated by the
determination of nitrate in Antarctic ice cores.

Item Type: Thesis (PhD)
Keywords: Ion exchange chromatography, Anion separation, Capillary liquid chromatography
Copyright Holders: The Author
Copyright Information:

Copyright 2001 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, 2001. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:50
Last Modified: 20 Jun 2017 01:39
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