There
are number of methods that are  utilized
to  bring separation between  the solute and the supercritical fluid, which
is acts  as the solvent. There are
mainly  three basic methods  that are be used to achieve this  separation.in  first case  the temperature or pressure is changed so tha
the solvent capability of the supercritical fluid is changed. The other
involves   “washing” the solute out of the supercritical
fluid  by using a solvent that can strip  out the solute from the supercritical fluid. Besides
 the separation of the solute from the
supercritical fluid, it is possible to separate many  solutes  using a packed column within the supercritical
fluid .

The
easiest  method to separate  the solute from a supercritical fluid is to
alter  the pressure of the supercritical
fluid so  as that either the fluid is no
more  supercritical or that the solute
looses the  solubility in the
supercritical fluid. Various scientists used this method to remove the solutes
of interest  from the supercritical
fluid. In all three methods ,the individuals performing the study routed the
solvent/solute combination through a restriction valve and then  into a collection vessel.the pressure is  reduced to room pressure inside the
collection vessel causing the supercritical fluid to return to its gas state
and the  release of solvent into the
collection vessel. Inside the collection vessel, the solute may be received by
the solvent  for further analyis. Other  times t to allow the crystallization of
solute the upon leaving the fluid the vessel is kept empty .Another change in
the  previous method involves changing
the temperature  to remove the solute
from the supercritical fluid. This may allow 
 the fluid to leave the
supercritical region, but in turn  allowing  pressure of the fluid to be maintained. .This  variation makes economic sense as it help to save
money by allowing the recirculartion  of
the pressurized fluid  without having to
repressurize it.. Lancas et al.
(1990) used  this method to remove the
respective solutes from the supercritical fluid. In  This method the solute is simply removed by
lowering the temperature of the solvent till the solute becomes insoluble and
precipitates out from the  fluid.
This  method or technique is called as  a cryogenic trap.The system is  depressurized as the extraction is complete  so as that extract is  removed from the  chamber.Additionally  solvent and s solute can be separated from
the supercritical fluid by “washing” allowing 
 for the process to be operated  at a constant pressure in a similar way as is
done in case of  cryogen
trap,Neverthless  it  allows for the removal of the solute from the
process without shutting  the process . the
above discussed removal is used  in green
coffee beans that involves removal caffeine from the supercritical CO2
(McHugh, 1994).

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now