Supercritical Fluid Chromatography
Supercritical fluids
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Occur above a critical temperature and a
critical pressure,
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Show both gaseous and liquid properties for
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Density
Diffusion coefficient and
Viscosity
Are very good solvents
Are frequently cheap, innocuous, non-toxic
Can easily be removed by evaporation
Give GC/LC hybrid behaviour – make great
mobile phases
Source:http://www.selectscience.net/products/analy
tical+preparative-sfc-instrument/?prodID=12418
SFC is particularly useful for analytes that are:
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Non-volatile
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Easily thermally-decomposed and/or
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Unsuitable for spectroscopic or electrochemical detection
and thus cannot be analysed by GC or HPLC
Created with MindGenius Business 2005®
Supercritical Fluid Chromatography
Mobile:Stationary phase equilibrium
Dependent on partition, strongly influenced by solvation power of the
supercritical fluid
Instrumentation: modified HPLC equipment:
 Thermostatted column oven
 Back-pressure device between column and detector (narrow capillary at end
of column)
 Detection may be conducted in gas phase
Mobile Phase
 Any supercritical fluid (commonly CO2, N2O, NH3, 1-Butane)
CO2 becomes supercritical at T>31ºC, P>7400KPa
Stationary Phase
 Variety, generally “cannibalised” from HPLC or GC
 May be packed (like HPLC)
 Or open-tubular siloxane coated (like GC)
Created with MindGenius Business 2005®
Supercritical Fluid Chromatography
Retention and Resolution
 Quicker than HPLC
 N similar to that for GC
 Suffers from band broadening (diffusion) like GC
Optimisation:
 Pressure  gives solvent power  and thus RT . e.g.(Hexadecane at 70atm
RT=25min, 90 atm RT=5min). May use gradient or isobaric elution.
 Temperature (for similar reasons)
 Organic modifiers (e.g. MeOH)
Detection
 Often uses HPLC detectors (UV etc)
 SFC allows easy interface with MS or IR
 Also allows use of Flame Ionisation Detector (FID)
 Eluent easily removed for further analysis
Applications
Wide range including: Drugs, foods, pesticides, polymers, surfactants….
Created with MindGenius Business 2005®