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Improved miniaturised solid phase extraction


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Candish, E 2015 , 'Improved miniaturised solid phase extraction', PhD thesis, University of Tasmania.

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The thesis focuses on the development of miniaturised solid phase extraction (SPE)
technologies for the rapid and effective processing of complex biological samples prior
to mass spectrometry (MS) analysis.
The first section focuses on the format and operation of miniaturised solid phase
extraction devices. The existing technology was queried and improved for a more
efficient operation. The miniaturised SPE technology, microextraction by packed
sorbent (MEPS), was explored as a representative format due to ease of operation. A
superior format of MEPS was developed that incorporates a two-way valve in the
syringe barrel for efficient sample and solvent introduction to the adsorbent bed.
Controlled directional flow (CDF)-MEPS allows fluid to be introduced directly into the
syringe barrel, bypassing the adsorbent bed entirely. Matching extraction workflows
demonstrated a reduction in carryover from 65% for conventional MEPS to only 1% for
CDF-MEPS. The developed technology was directly hyphenated with electrospray
ionisation (ESI)-MS and sharp, concentrated sample bands were revealed.
The second section of this thesis explores the concept of organic polymer monolith
adsorbents for improved miniaturised SPE. Polymer monoliths are widely described as
adsorbents for SPE but appropriate characterisation of physical characteristics is rarely
explored to probe any observed advantages and disadvantages over alternative
adsorbents. Fabrication of large surface area adsorbent involved a high percentage of
the crosslinking monomer, divinyl benzene (DVB), or the hypercrosslinking of preformed
polymer. Frontal analysis studied the adsorption of probes; anisole, phenol and
cortisone. Extraction performance was compared with conventional polymer particulate
adsorbents. The polymer monolith adsorbents demonstrated a clear advantage for the small probes, as a high extraction performance (high recovery) could be achieved
independent of flow rate. Limited retention of cortisone was seen for both polymer
monolith adsorbents as the surface area was predominantly provided by micropores
inaccessible to the larger probe cortisone.
The size exclusion mechanism of the microporous large surface area poly(DVB) was
exploited as it presented a physical barrier restricting proteins from accessing the
adsorbent’s internal surface. A hydrophilic layer of poly(ethylene glycol) methacrylate
(PEGMA) was grafted to the residual vinyl groups of the poly(DVB) and their
suitability as restricted access materials was explored. PEGMA monomers with glycol
chain lengths of Mn 360 and 950 were studied. The external hydrophilic layer was
delicately balanced to prevent protein binding while preserving the hydrophobic
capacity and rapid analyte mass transfer. Sharp breakthrough curves confirmed that
both hydrophobic capacity and rapid analyte mass transfer were maintained for
poly(DVB)-g-PEGMA950, while the adsorbent displayed a substantial reduction in
protein binding. Ibuprofen was extracted from human plasma (diluted 20% v/v), using
both poly(DVB) and poly(DVB)-g-PEGMA950. The extracts were analysed by at-line
ESI-MS. The sample from prepared with the biocompatible poly(DVB)-g-PEGMA950
provided extracts with reduced protein content resulting in a more sensitive and
improved at-line ESI-MS analyses.

Item Type: Thesis - PhD
Authors/Creators:Candish, E
Copyright Holders: The Author
Copyright Information:

Copyright 2015 the author

Additional Information:

Chapter 2 appears to be the equivalent of a post article finally published as: Candish. E. Gooley, A., Wirth, H-J., Dawes, P. A., Shellie, R. A. & Hilder, E. F. 2012. A simplified approach to direct SPE-MS. J. Sep. Sci. 35, 2399–2406

Chapter 3 appears to be the equivalent of a post-print article finally published as: Candish, E., Wirth, H.J., Gooley, A. A., Shellie, R. A., Hilder, E.F., 2015, Characterization of large surface area polymer monoliths and their utility for rapid, selective solid phase extraction for improved sample clean up, Journal of Chromatography A, 1410, 9-18, 10.1016/j.chroma.2015.07.065

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