Page 36 - LC-SFC_Pharma_Brochure

The extraction conditions can be conÿgured such that the pretreat- (2) Static extraction
ment operations can be run from the same LabSolutions workstation Once the extraction vessel has reached the set temperature, the su-
used for the analysis. Thus, the extraction conditions and pretreat- percritical uid is introduced into the vessel and static extraction
ment can be intuitively controlled in the same way as sample analysis. occurs. Parameters such as the extraction vessel temperature, pres-
The material extracted by the supercritical uid is collected in a trap sure and duration of the extraction, and type and quantity of the
column, subsequently eluted by an organic solvent, and ÿnally recov- modiÿer can be independently controlled during extraction depend-
ered using a fraction collector before performing the analysis by LC ing on the sample and target constituent to be extracted.
(LC/MS), GC (GC/MS), or NMR. Comprehensive and complementary (3) Dynamic extraction
sample analysis can be achieved by combining the results from sever- After the static extraction, a dynamic extraction is performed by deliver-
al of these analysis methods.
ing the uid through the extraction vessel. This operation allows the ex-
Compared with Soxhlet extraction, SFE uses a much lower quantity of traction of the target material from the extraction vessel and subsequent
organic solvent during the pretreatment, thereby reducing costs and collection in a trap column located downstream of a back pressure regu-
allowing a more environmentally friendly pretreatment step. lator. Downstream of the back pressure regulator is held at close to at-
mospheric pressure such that carbon dioxide is in a gaseous state while
collecting the extraction material in the trap column. ODS and other col-
3. Operating Principles of the Nexera UC umns used for HPLC can be used as trap columns. Similar to static extrac-
SFE Pretreatment System tion, the extraction vessel temperature, pressure and duration of the ex-
traction, and type and quantity of the modiÿer can be adjusted depend-
The schematic diagrams of the Nexera UC SFE pretreatment system
showing material ow and principle of operation are shown in Fig. 4. ing on the sample and target constituent to be extracted.
The extraction process can be roughly divided into four operations: (4) Elution from the trap column and recovery of the extraction material
(1) Extraction vessel delivery and temperature control Once the dynamic extraction has ÿnished, the uid delivery is stopped and
the back pressure regulator is opened, thereby allowing the system pres-
An extraction vessel is moved from the rack changer to the SFE unit,
and the extraction vessel is subsequently heated to the set tempera- sure to drop to atmospheric pressure. The delivery pump is then switched
ture (40–80 ºC). from the modiÿer to the eluent, which is passed through the trap column
to elute the extraction material. The eluate is then recovered into collec-
tion tubes using a fraction collector. An organic solvent is used as the
eluent to simplify concentration and post-treatment steps of the eluate.

CO2 pump Back pressure Fraction
SFE unit regulator Column oven collector
(1) Extraction vessel delivery and temperature control
CO2
A speciÿed extraction vessel is transferred to the SFE unit and cylinder
Solvent
heated to the set temperature. delivery pump
Trap column
Collection
Extraction vessel tubes
Modi er Eluent
(2) Static extraction
When the temperature of the extraction vessel has reached the set
temperature, the supercritical uid is introduced and static extrac-
tion (i.e., in the absence of uid ow) is allowed.

(3) Dynamic extraction
The extraction is dynamically performed by passing the supercriti-
cal uid through the extraction vessel. The extraction material is
taken from the extraction vessel and collected at atmospheric pres-
sure after evaporation of CO2 in the trap column downstream the
back pressure regulator.

(4) Elution from the trap column and recovery of the extrac-
tion material
The delivery pump is used to deliver the eluent through the trap
column, thereby eluting the extraction material, which is then re-
covered using a fraction collector.

Fig. 4 Material Flow and Principle of Operation

2