Open Access Repository

Mixed-mode electrokinetic chromatography of low molecular weight anions and cations

Downloads

Downloads per month over past year

Zakaria, Philip (2003) Mixed-mode electrokinetic chromatography of low molecular weight anions and cations. PhD thesis, University of Tasmania.

[img]
Preview
PDF (Whole thesis)
whole_ZakariaPh...pdf | Download (7MB)
Available under University of Tasmania Standard License.

| Preview

Abstract

This work presents a comprehensive study into selectivity control over electrokinetic
chromatography (EKC) systems for the determination of small organic anions and
cations using various additives.
For the separation of anions an electrolyte system comprising a cationic soluble
polymer (poly( diallydimethylammonium chloride), PDDAC) and a neutral
ß-cyclodextrin (ß-CD) as pseudo-stationary phases was used. The separation
mechanism was a combination of electrophoresis, ion-exchange (IE) interactions with
PDDAC, and hydrophobic interactions with ß-CD. The extent of each
chromatographic interaction was independently variable, allowing for control of the
separation selectivity of the system.
Various cationic analytes were also examined, including opiate alkaloids, aromatic
bases and amino acids. In the case of the opiate alkaloids (morphine, thebaine,
10-hydroxy thebaine, codeine, oripavine and laudanine) a system utilising
sulfated-ß-cyclodextrin (s-ß-C:P) as a pseudo-stationary phase was used.
Cation-exchange interactions between the cationic analytes and the anionic s-ß-CD
(7-11 moles of sulfate groups per mole CD) were found to be the predominant
separation mechanism.
The separation of a series of aromatic bases was achieved utilising an electrolyte
system comprising an anionic soluble polymer (polyvinylsulfonic acid, PVS) and
ß-CD as pseudo-stationary phases. The separation mechanism was based on a
combination of electrophoresis, IE interactions with PVS, and hydrophobic
interactions with ß-CD. The extent of each chromatographic interaction was
independently variable, allowing for control of the separation selectivity of the system. The IE and the hydrophobic ~teractions could be varied by changing the
concentrations of PVS and ß-CD, respectively. Additionally, mobilities of the bases
could be controlled by varying pH, due to their large range of pKa values.
Selectivity control of the enantiomeric separation of the three aromatic amino acids
(phenylalanine, tyrosine and tryptophan) was demonstrated utilising temperature and
s-ß-CD and dextran sulfate as pseudo-stationary phases. Two systems were explored
using s-ß-CD as the chiral selector. In these systems either temperature or the
addition of dextran sulfate was used to increase the selectivity control.
The possibility of the simultaneous separation of anions and cations was demonstrated
using a series of aromatic carboxylic acids, sulfonates and opiates as analytes.
Separation was achieved using electrokinetic chromatography employing a mixture of
PDDAC and the amphiphilic anion hexanesulfonate as pseudo-stationary phases. In
this system, the PDDAC pseudo-stationary phase interacted with the anionic analytes,
whereas the hexanesulfonate interacted with the cationic analytes. A further
interaction between the combined PDDAC-hexanesulfonate complex and the more
hydrophobic analytes was also evident.
Mathematical modelling based on physical equilibrium and artificial neural networks
was also undertaken, with the models successfully describing each system (r2>0.98
for predicted versus observed migration times). The models were then used to not
only optimise each system, but also to allow predictable selectivity control leading to
attainment of desired migration orders.

Item Type: Thesis (PhD)
Keywords: Electrokinetics, Addition polymerization, Chromatographic analysis, Anion separation, Cations
Copyright Holders: The Author
Copyright Information:

Copyright 2003 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, 2003. Includes bibliographical references

Date Deposited: 04 Feb 2015 23:29
Last Modified: 24 Aug 2016 04:25
Item Statistics: View statistics for this item

Actions (login required)

Item Control Page Item Control Page
TOP