Source: Phasex Corporation website'

1
Source Phasex Corporation website.
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Source Skoog, Holler, and Nieman, Principles of
Instrumental Analysis, 5th edition, Saunders
College Publishing.
Supercritical fluids have viscosity and
diffusivity intermediate between liquids and
gases. They can also dissolve things,
like liquids can. What does this mean for
chromatography?
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SFC characteristics Faster linear velocity than
LC Greater separation efficiency per unit time
than LC Greater solute solubility than
GC Greater mobile phase selectivity than
GC Advantages compared to LC or GC Compared to
GC Can separate thermally unstable
compounds Can separate compounds beyond
the volatility range of GC Compared to
LC Reduced analysis time
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Comparison of MW elution ranges for different
types of column chromatography
Source Skoog, Holler, and Nieman, Principles of
Instrumental Analysis, 5th edition, Saunders
College Publishing.
5
Demonstration of efficiency advantages of SFC
compared to LC.
Source Skoog, Holler, and Nieman, Principles of
Instrumental Analysis, 5th edition, Saunders
College Publishing.
6
Source Skoog, Holler, and Nieman, Principles of
Instrumental Analysis, 5th edition, Saunders
College Publishing.
7
SFC mainly uses carbon dioxide Convenient
critical parameters Tc 31C Pc 72 atm (1080
psi) Cheap Safe Minimize use of organic
solvents Typically operate up to 150C and
10,000 psi
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SFC with Carbon Dioxide Limited to nonpolar
solutes Some polarity adjustment by adding 5-20
organic cosolvents (called modifiers) Main
uses are as alternative to normal-phase LC
and for chiral separations.
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Schematic of SFC Instrumentation
Source Skoog, Holler, and Nieman, Principles of
Instrumental Analysis, 5th edition, Saunders
College Publishing.
10
Instrument Features Pumps pressure control
rather than flow control mainly use syringe
(displacement) pumps Injection use LC-type
valve injectors with capillary columns, flow
(or time) splitting Detectors use full range of
GC and LC detectors advantage with FID
solvating mobile phase combined with universal
detection
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With SFC, gradient or temperature programming can
be used, but pressure programming is much
easier and much more common.
Source Skoog, Holler, and Nieman, Principles of
Instrumental Analysis, 5th edition, Saunders
College Publishing.
12
Can supercritical fluids be used in other areas
to replace solvents? Yes extraction, cleaning,
processing, reactions, etc.