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Studies on separation selectivity in capillary zone electrophoresis of inorganic anions

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Harakuwe, AHH (1995) Studies on separation selectivity in capillary zone electrophoresis of inorganic anions. PhD thesis, University of Tasmania.

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Abstract

Parameters influencing the separation selectivity of low molecular-mass anions using
free-solution reversed electroosmotic flow capillary zone electrophoresis (F'RECZE)
have been studied. First, detailed preliminary investigations were performed to address
two major limitations of FRECZE, namely, imprecision in migration times and
variability of phosphate response. A capillary conditioning regime suitable for the
generation of stable migration times and optimal phosphate response was developed.
Also, it was established that dried electroosmotic flow (EOF) modifiers generated more
stable migration times and gave improved resolution. Second, a wide range of selectivity-influencing parameters was studied. These
parameters included electrolyte pH, EOF modifier chain length, nature of the EOF
modifier counter-anion, EOF modifier concentration, binary EOF modifier mixtures,
type of indirect detection probe, probe concentration, 1-butanol as an electrolyte
additive, and instrumental variables (e.g. detection wavelength and separation voltage).
The trends of migration order observed with the above parameters are discussed and
possible mechanisms outlined. Major migration order changes were caused by pH and
EOF modifier effects. Electrolyte pH variation changed the migration order of weak
acid anions at pH values close to their pKa points by altering their charge to mass
ratios. Migration order changes due to either increased or reduced ion-pairing effects
were pronounced for lipophilic anions and could be induced particularly with EOF
modifier changes, electrolyte concentration and 1-butanol as additive. Migration order
changes due to increased effective charge of anions were influenced particularly by 1-
butanol as additive as well as electrolyte ionic strength. Third, information from the above studies was applied to the separation of inorganic
anions in samples having varying levels of matrix complexity, e.g. tap water, Bayer
liquor, acid-digested concrete, toothpaste, urine, a formulation for prevention of gallstone
formation, corned beef, seawater and Antarctic saline lake water. Analytical
performance characteristics are discussed for the separation of anions in Bayer liquor,
concrete and toothpaste.
The highlights of this study were that the useful pH range of chromate-based electrolyte
could be extended by 20% by incorporation of 1-butanol in the electrolyte; the
resolution between fluoride and phosphate could be improved by over 400% making
possible the separation of 1 gg.mL-1fluoride in the presence of over 800 p.g.mL-1
phosphate, and the use of binary EOF modifier mixtures was introduced and applied to
the analysis of Bayer liquor. Two electrolyte compositions capable of simultaneously
separating chloride, sulfate, oxalate, malonate, fluoride, formate, phosphate, succinate,
tartrate, carbonate and acetate in under 4 minutes were identified. Calibrations were
linear in the range 1 - 10 j.tg.tnL-1 , detection limits as low as 0.09 lig.mL-1 were
obtained and near quantitative recoveries (except for phosphate) were recorded.

Item Type: Thesis (PhD)
Keywords: Capillary electrophoresis, Anion separation
Copyright Holders: The Author
Copyright Information:

Copyright 1995 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, 1996. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:01
Last Modified: 23 May 2017 01:36
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