Analytical Chemistry
in Supercritical Fluids
Introduction
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Supercritical fluids are a main interest of the Clean Technology Research
Group. The fluids provide an excellent method for separating complex mixtures
of thermally unstable but environmentally important compounds (e.g. pollutants,
pesticide residues, polymer additives etc.).
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We have combined spectroscopic detection, particularly FTIR, with supercritical
chromatography so that the components can be identified after they have
been separated.
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The system is now being combined with supercritical fluid extraction, UV
spectroscopy and mass spectrometry for more complete identification of
products.
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Practical applications include removal of toxic residues from dental plates
and forensic analysis of cannabinoids.
Supercritical Fluid Chromatography - Mass Spectrometric Speciation
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Capillary Supercritical Fluid Chromatography (cSFC) is an extremely sensitive
technique (even with a technique as insensitive as FTIR we have detected
as little as 95 pg. of caffeine injected onto the column) However, cSFC
columns are very easily overloaded.
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By contrast packed column SFC (pSFC) has a much wider dynamic range without
overloading but interfacing conventional EI or CI mass spectrometry to
pSFC is technically much more difficult than for cSFC.
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Our solution has been to use atmospheric-pressure chemical-ionisation (APCI)
mass spectrometry. The technical problems have been substantial but our
current results with industrially significant polymer additives are now
extremely encouraging. The key point is that we can vary conditions at
will so that either we observe the parent ions or we obtain an extensive
and informative fragmentation pattern.
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pSFC-APCI/MS is a new technique. As far as we are aware our instrument
is the only one of its type in the UK, one of few in the world. We are
now establishing its capabilities and to apply it to a wide range of analytical
problems. The main activity at present is a co-operative research programme,
funded by the European Union, involving industrial concerns in the U.K.,
Germany and France, and the New University of Lisbon. This aims to establish
procedures for the supercritical extraction and encapsulation of a range
of natural products of interest in the pharmaceutical, food, flavour and
fragrance industries.
Further Information
For further information please contact G.
Davidson
Key Publications from Nottingham
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A Capillary SFC-FTIR study of triglycerides, Kaplan, M., Davidson, G. &
Poliakoff, M., J. Chromatogr., 1994, A, 673, 231-237.
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Vibrational Spectroscopy in Supercritical Fluids:- from Analysis and Hydrogen-Bonding
to Polymers and Synthesis, Poliakoff, M., Kazarian S.G. & Howdle, S.M.,
Angewandte Chemie, 1995, 34, 1275-95.
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A Preliminary Study of the Analysis of Cannabis by Supercritical Fluid
Chromatography with Atmospheric Pressure Chemical Ionisation Mass Spectroscopic
Detection, Backstrom, B,; Cole, M. D.; Carrot, M. J.; Jones, D. C.; Davidson.
G.; Coleman, K; Science and Justice, 1997, 37, No.2, 91-97
Supercritical fluid extraction and chromatography of non-ionic surfactants
combined with FTIR, APCI-MS and FID detection. Auerbach RH, Dost K, Jones
DC, Davidson G. Analyst, 1999, 1501-1505.
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Determination of pesticides in soil samples by supercritical fluid chromatography-atmospheric
pressure chemical ionisation mass spectrometric detection.
Dost K, Jones DC, Auerbach R, Davidson G. Analyst, 2000,
125, 1751-1755.
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Page created by: Simon Poliakoff
Created: July 1997
Last Revised: January 2001