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Our Research |
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Separations & Chromatography Research Group
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Lateefa Al-Khateeb | Katherine Ridgeway |
Our laboratory has shown that "superheated" (sub-critical) water can be used, without organic modifiers, as a mobile phase for reversed-phase high performance liquid chromatography (RP-HPLC). In a conventional RP-HPLC system, water is viewed as the weakest solvent because it is the most polar solvent in common use. However, the polarity of water can be significantly decreased while heating under pressure; to match the polarity of conventional organic/aqueous mobile phases. An example: the chromatogram on the Analytical Chemistry Section home page shows the separation of three aryl ketones, with pure, superheated water as mobile phase at 200 °C and a polystyrene-divinylbenzene column as stationary phase. The ketones elute in a true reversed-phase mode, their order being: 1. m-hydroxyacetophenone, 2. acetophenone and 3. m-methylacetophenone. Superheated water offers an enhanced separation, producing greater efficiencies and improved resolution. Such a system is easy to operate, with only minor adjustments being necessary to the set up of the HPLC system itself. The use of a superheated water mobile phase could offer a number of important benefits; perhaps most importantly the environmental and monetary reasons for its preferred use. It could also present chromatographers with additional advantages, such as the use of low wavelength UV detection or flame-based GC detectors, as well as the prospects of enhanced separations through increased efficiencies. A particularly interesting aspect has been the linkage of superheated heavy water (D2O) with NMR (NMR-MS) to give interference free on-line NMR spectra.
The aqueous mobile phase also enables the flame ionisation detector to be employed as a novel universal and sensitive detector for liquid chromatography. For the first time it has been possible to directly transfer the eluent to the FID avoiding the use of evaporative or transport interfaces. This work has been highly successfully and has lead to the formation of Phlogiston Scientific Ltd as a university spin out company with Professor Smith, his former research student Joanne R. Bone, and Dr Barry Sharp.
The success of the superheated water project has lead to a number of further
studies into separations and extractions at elevated temperatures. This
work is challenging many of the original ideas governing the use of high
temperatures in liquid chromatography and of its supposed benefits. The
introduction of new stable hybrid stationary phases has led to various
thermodynamic studies of retention mechanisms and the effects of pressure
during chromatographic separation.
Temperature programming has been utilized for the separation of complex
mixtures to increase peak capacity and efficiency equivalent to gradient
elution. This has included the testing of various detection methods, where
a temperature gradient is desirable as baseline is unaffected.
Two-Dimensional Liquid Chromatography is rapidly gaining importance for the analysis of complex samples, due to the considerable increase in resolving power that can be achieved, providing the retention mechanisms in the two dimensions are orthogonal. The approach to two-dimensional analysis is underway, where preliminary “heart-cutting” chromatography is employed in the first dimension separation. Each band produced in the first dimension column is then selectively isolated and collected, and subsequently subjected to a second dimension separation. Several stationary phases displaying various degree of selectivity are being evaluated in the second dimension. In order to achieve orthogonal separation the influence of the primary column retention (hydrophobicity) is minimised in the second dimension by choosing among secondary columns amino and cyano stationary phases.
Capillary electrochromatography, a hybrid technique between capillary
electrophoresis (CE) and high performance liquid chromatography (HPLC),
is a new separation technique which has evolved recently. This technique
is promising to be powerful since it enjoys the combined advantages of
CE and HPLC. However, its development is hampered by the problem of bubble
formation and of variation of electroosmotic flow with different stationary
phases. It is therefore the aim of this project to produce packed capillaries,
which can be employed in Capillary Electrochromatography (CEC). Ion exchangers
will also be evaluated as stationary phases in CEC, and hopefully, both
ionic and neutral analytes can be separated on these phases. Work in this
area is directed towards forensic applications and chemotaxonomic studies
of a noxious weed.
Over recent years there has been an increased interest in the potential of supercritical fluids such as carbon dioxide as a mobile phase for chromatography and for extraction. Studies are being carried out into an understanding of their role compared to liquid chromatography. The scope of extraction with supercritical fluids is being explored and its application to areas, such as herbal medicines is being investigated.
Studies are under way to examine the application of chromatography to
a number of areas including pesticide analysis and fine chemicals. In
each case the aim is to develop new methods and to explore the range of
method applications. This work has included new derivatisation methods
and new detectors. Many of these projects have been supported by industrial
companies as well as Research Council funds.
I come from Oman. I am currently employed by the forensic department for
the Royal Oman Police who are also sponsoring my PhD. I completed my MSc
degree in Analytical and Pharmaceutical Science at Loughborough University.
Since October 2004, I have been working on a project for the preparation
of monolithic columns with forensic applications using HPLC and CE.
e-mail: F.Al-harthy@lboro.ac.uk
I am from Malaysia. I graduated in Chemical Engineering from the University
of Missouri- Columbia, USA in 1999 and then started working as a chemist
for a pharmaceutical company in north Malaysia. Subsequently, in 2001
I joined the Malaysian Rubber Board (MRB) as a Research Officer. In MRB
I am part of the Material Characterization Unit which operates for both
researchers and rubber related manufacturers. I am studying the analysis
sulphur containing additives in rubber products using metal ion complexation
and superheated water chromatography.
e-mail: R.Che-Isa@lboro.ac.uk
I am from Saudi Arabia. I graduated with a BSc in Chemistry at King Abdul Aziz University in Jeddah, where I also obtained my MSc degree in Ion selective electrodes. I worked in analytical chemistry in King Abdul Aziz University as as demonstrator. In October 2002 I joined Prof. R. M. Smith's research group as a PhD student. My research project is on the effects of high temperature and pressure in HPLC in particular the differences between the properties of the thermally hybrid stationary phases.
e-mail: L.Al-Khateeb@lboro.ac.uk
I'm from Saudi Arabia. I graduated from the Chemistry Department at King
Abdul Aziz University in 1996. I joined the United State Geological Survey
(USGS) working as an analyst. In 2001 I returned to Academia as demonstrator
in the Medicinal Chemistry Department. II then attended Newcastle University
in 2003/2004 to undertake an MSc in Medicinal Chemistry. My research project
is on sideroxylonal drugs and studies of eucalyptus plant extracts by
HPLC and SFE and I hope to also examine some drug compounds using high
temperature chromatography.
e-mail: H.Albishri@lboro.ac.uk
I graduated with a BSc in Biochemistry from King Saud University in Riyadh, Saudi Arabia. Since then I joined the Forensic Science Department in my country as a questioned documents examiner. In December 2004 I joined Prof. R. M. Smith's research group as a PhD student. My research project is the quantitative determination of elemental sulfur in plant materials by GC-MS.
e-mail: A.Swidan@lboro.ac.uk
I obtained my BSc and MSc degrees in Analytical Chemistry from Rivers State University of Science & Technology, Nigeria and Northumbria University respectively. Attracted by the medicinal properties of Fallopia japonica (a native plant of Japan and N. China), I am undertaking a PhD in this subject. I am currently using Micellar Electrokinetic Chromatography to investigate the pharmacologically active components of this plant.
e-mail: E.Young@lboro.ac.uk
I graduated with a BSc (Hons) in Applied Chemistry from De Montfort University, Leicester. I then completed a MSc degree in Analytical Chemistry & Instrumentation at Loughborough University in 2000/2001. I have worked for several major Pharmaceutical companies in analytical R&D. currently I am being sponsored by GSK R&D Ltd to carry out research in to the development of a resistively heated oven, designed for isothermal and temperature programmed fast LC applications.
e-mail: F.Harvey-Doyle@lboro.ac.uk
I am originally from Italy, where I graduated with a Bachelor in Science at the University of Parma. I moved to England and started a degree course on a part-time basis whilst working within the analytical chemistry industry. I graduated with a BSc in applied chemistry from Nottingham Trent University and moved on to work as analytical chemist for several pharmaceutical companies. I joined Loughborough University and am working on a 3M Healthcare funded project on comprehensive multidimensional liquid chromatography for potential drug excipients.
e-mail: M.L.Dolci@lboro.ac.uk