184
L. Brown et al.
conventional CCC and LLC instruments. The ILLC equipment uses coils that are
made from stainless steel (rather than PTFE/poly(vinyl alcohol) (PVA)), and the
main pressure bottlenecks in the solvent flow pathways have been removed [15].
ILLC has been found to be a very versatile separation technology and allows a very
wide range of separations to be performed. Examples include the direct separation
of metal(II) salts, saccharides, polysaccharides, triglycerides, petrochemicals, and
terpenes [14b, 16, 38].
By the modification of the structure and therefore properties of ionic liquids,
they can be designed or selected for use in any given separation. The viscosity,
density, density difference, interfacial tension, and relative solubility of solutes can
all be adjusted through alterations to the structure of the ionic liquid anion or cation.
Hence, ILLC allows the separation of practically any soluble mixture, provided that
a suitable two-phase solvent system can be designed or found. ILLC can, therefore,
be described as using “designer solvents for designer separations”. Whilst this area
of research is still relatively new, ILLC has the potential to allow separations to be
carried out which are currently considered to be either too difficult or too expensive
to perform on a large scale. Compounds that are thought to be too insoluble or too
immiscible with biphasic molecular solvent systems can now be separated by ILLC.
An example of this is with the purification of lentinan [26b], in which the scale of
the separation was boosted from the tens of milligrams [71] to the gram scale, using
a similar-sized apparatus. With larger capacity ILLC instruments, including CPC
instruments, much larger scale separations can be achieved.
There can be no doubt that having been a Cinderella project for many decades,
CCC/CPC is now maturing into not only a valuable laboratory preparative technique
but also into a pilot and large-scale process technique [25, 72]. Instrumentation has
been developed capable of laboratory, pilot, and large-scale process applications
with both standard biphasic solvents and ionic liquid biphasic solvents [15, 26b].
Similarly, ionic liquid research and technology has moved from an electrochemical
curiosity in the 1980s to a new scientific discipline in its own right, and it is being
deployed in industry on process scales [9b, 73].
The full potential of combining both ionic liquid and countercurrent chromatography technologies is beginning to be realized. This union massively increases the
potential number of solvent systems available in CCC separations, and concomitantly
leads to a greater understanding of ionic liquid phase behavior that can be applied
to separations that were once not thought possible on a large scale. Liquid–liquid
CCC/CPC research has been carried out by many non-ionic liquid specialists, and
they have expressed concern to AECS-QuikPrep Ltd. that certain ionic liquids can
degrade various chemical structures and compounds. As in the case with lentinan,
there are a vast number of options for the choice of ionic liquids and usually many can
be found that do not react with or denature compounds being separated. Ionic liquids
once purchased off-the-shelf or custom-synthesized can be recycled and cleaned up
at minimal cost [74].
Peptides, proteins, monoclonal antibodies (mAb’s), enzymes, bioactive compounds, precious metals, actinides, and lanthanides are all ideal candidates for ionic
liquid-CCC/CPC separation processes, as all are high value but can be potentially
L. Brown et al.
conventional CCC and LLC instruments. The ILLC equipment uses coils that are
made from stainless steel (rather than PTFE/poly(vinyl alcohol) (PVA)), and the
main pressure bottlenecks in the solvent flow pathways have been removed [15].
ILLC has been found to be a very versatile separation technology and allows a very
wide range of separations to be performed. Examples include the direct separation
of metal(II) salts, saccharides, polysaccharides, triglycerides, petrochemicals, and
terpenes [14b, 16, 38].
By the modification of the structure and therefore properties of ionic liquids,
they can be designed or selected for use in any given separation. The viscosity,
density, density difference, interfacial tension, and relative solubility of solutes can
all be adjusted through alterations to the structure of the ionic liquid anion or cation.
Hence, ILLC allows the separation of practically any soluble mixture, provided that
a suitable two-phase solvent system can be designed or found. ILLC can, therefore,
be described as using “designer solvents for designer separations”. Whilst this area
of research is still relatively new, ILLC has the potential to allow separations to be
carried out which are currently considered to be either too difficult or too expensive
to perform on a large scale. Compounds that are thought to be too insoluble or too
immiscible with biphasic molecular solvent systems can now be separated by ILLC.
An example of this is with the purification of lentinan [26b], in which the scale of
the separation was boosted from the tens of milligrams [71] to the gram scale, using
a similar-sized apparatus. With larger capacity ILLC instruments, including CPC
instruments, much larger scale separations can be achieved.
There can be no doubt that having been a Cinderella project for many decades,
CCC/CPC is now maturing into not only a valuable laboratory preparative technique
but also into a pilot and large-scale process technique [25, 72]. Instrumentation has
been developed capable of laboratory, pilot, and large-scale process applications
with both standard biphasic solvents and ionic liquid biphasic solvents [15, 26b].
Similarly, ionic liquid research and technology has moved from an electrochemical
curiosity in the 1980s to a new scientific discipline in its own right, and it is being
deployed in industry on process scales [9b, 73].
The full potential of combining both ionic liquid and countercurrent chromatography technologies is beginning to be realized. This union massively increases the
potential number of solvent systems available in CCC separations, and concomitantly
leads to a greater understanding of ionic liquid phase behavior that can be applied
to separations that were once not thought possible on a large scale. Liquid–liquid
CCC/CPC research has been carried out by many non-ionic liquid specialists, and
they have expressed concern to AECS-QuikPrep Ltd. that certain ionic liquids can
degrade various chemical structures and compounds. As in the case with lentinan,
there are a vast number of options for the choice of ionic liquids and usually many can
be found that do not react with or denature compounds being separated. Ionic liquids
once purchased off-the-shelf or custom-synthesized can be recycled and cleaned up
at minimal cost [74].
Peptides, proteins, monoclonal antibodies (mAb’s), enzymes, bioactive compounds, precious metals, actinides, and lanthanides are all ideal candidates for ionic
liquid-CCC/CPC separation processes, as all are high value but can be potentially