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Analysis of pharmaceuticals in environmental water samples by capillary elctrophoresis

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Dawod, Mohamed Dawod Zakaria (2010) Analysis of pharmaceuticals in environmental water samples by capillary elctrophoresis. PhD thesis, University of Tasmania.

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Abstract

Capillary electrophoresis (CE) has been used for decades for the determination of
different classes of pharmaceuticals in different sample matrices because of its
advantageous high separation efficiency and fast analysis time. However, the major
disadvantage of CE is its poor detection sensitivity. In the current work, the
improvement in detection sensitivity of CE has been extensively studied and applied
for the determination of two classes of pharmaceutical compounds.
Electrokinetic supercharging (EKS), a powerful preconcentration technique in CE,
has been studied for the analysis of seven non-steroidal anti-inflammatory drugs
(NSAIDs). The separation selectivity was optimised via adjustment of the
concentration of the separation buffer (disodium tetraborate pH 9.20) and the
amount of methanol as an organic modifier. Different EKS parameters, including
injection voltage, injection time, and amounts of leading and terminating
electrolytes were studied. The optimised conditions allowed detection sensitivity to
be improved by 2,400-fold when compared to field-amplified sample stacking (FASS)
and the limits of detection (LODs) were down to 50 ng/L.
A valuable modification to the EKS system, namely counter-flow EKS (CF-EKS), has
been developed in order to decrease the amount of the interfering sample matrix
involved in the system, hence, larger amount of analytes could be concentrated.
Computer simulation studies were undertaken in order to understand the trends in sensitivity enhancement from EKS to CF-EKS. After assigning the optimal counter
pressure and injection voltage in CF-EKS, an artificial neural network (ANN) was
developed for optimising the injection time and the amount of terminating
electrolyte. Upon comparison with FASS, the optimal conditions of CF-EKS allowed
the sensitivity to be enhanced by 11,800-fold and the LODs were decreased to 10.70
ng/L for the studied NSAIDs.
The on-line hyphenation of EKS-CE with the highly precise electrospray ionisation
mass spectrometry (ESI-MS) was for the first time investigated, and then applied for
the determination of five acidic hypolipidaemic drugs. The separation was
performed in a co-electroosmotic flow (co-EOF) mode using the EOF reversal agent
hexadimethrine bromide (HDMB) in ammonium bicarbonate buffer pH 9.00. An
ANN was developed for the optimisation of the separation selectivity, and the EKS-ESI-MS
system provided enhancement in detection sensitivity of 1,000-fold when
compared to FASS. The LODs for the studied hypolipidaemic drugs were decreased
to 180 ng/L.
Simultaneous separation of charged and neutral hypolipidaemic drugs was made
possible by the application of micellar electrokinetic chromatography (MEKC).
Ammonium bicarbonate pH 8.50 was used as a separation electrolyte and sodium
dodecyl sulfate (SDS) was used as a micelle-forming agent. In order to enhance the
detection sensitivity in MEKC, three on-line preconcentration strategies, namely
sweeping, analyte focusing by micelle collapse (AFMC) and simultaneous FASS-sweeping were investigated and applied for the determination of eight
hypolipidaemic drugs. When compared with a hydrodynamic injection (5 s at 50
mbar, 0.51% of capillary volume to detection window) of drug mixture prepared in
the separation background electrolyte (BGE), improvements in detection sensitivity
were 60, 83, and 80-fold for sweeping, AFMC, and FASS, respectively.
Finally, all the developed on-line preconcentration techniques were successfully
tested for quantitative repeatability, and then applied for the determination of
target analytes in wastewater as well as drinking water samples from Hobart city -
Australia.

Item Type: Thesis (PhD)
Copyright Holders: The Author
Copyright Information:

Copyright 2010 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:

Available for use in the Library and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2010. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:14
Last Modified: 11 Mar 2016 05:53
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