Lab #8: SFE
Introduction:
Supercritical fluid extraction (SFE) is a process of separating one component from another using
supercritical fluids as the extracting solvent. The component being extracted is called the extractant and
what the extractant is being extracted from is called the matrix. Usually the extraction is from a solid
matrix, but a liquid matrix can be used as well. The SFE consists of a tank of the mobile phase, which is
usually CO2, a pump to pressurize the gas, an oven containing the extraction vessel, a restrictor to
maintain a high pressure in the extraction line, and a trapping vessel. Analytes are trapped by letting the
solute-containing supercritical fluid decompress into an empty vial, through a solvent, or onto a solid
sorbent material. SFE extractions can be done in a dynamic, static, or combination of both.
Purpose:
The purpose of this lab is to extract paraffin wax from paper used in food packaging.
Procedure:
Cleaning Procedure
1. The recirculator needs to be turned on. This is the separate system on the far left that has hoses
containing coolant running to and from it. The recirculator needs to run for a minimum of ten
minutes before starting any experiments.
2. Check the Erlenmeyer flask labeled methanol. There should be enough methanol in the
Erlenmeyer to have the head of the pump hose completely submerged. Replenish the methanol
as necessary.
3. Turn on the cleaning pump (the unit on the immediate left of the SFE). The switch is located on
the back side of the unit.
4. Check inlet, outlet and the vent valves to make sure they are all closed. Close them if necessary,
then turn on the four switches on the front side of the SFE. You WILL hear an alarm sound, this is
normal.
5. Take the sample vessel (the steel container with the ends that screw on) and open it. Place
about quarter amount of glass wool in the vessel and pack it using the metal rod.
6. Place the vessel into the oven of the SFE and screw then valves into the proper ends of the
vessel. If these are not tight, the vessel will leak and you will lose pressure. Do not forget to
place the temperature probe against the vessel in the grooves.
7. Set the oven temperature to 100 C and the valve temperature to 110 C.
8. Turn on the CO2 tank (the valve directly on the tank first, then open the lines with the red
handle) and use the knob on the front of the SFE to set the pressure to 240 bar.
9. Allow the oven and valve temperatures to reach their set point. Once they reach their
temperatures, open the inlet valve and you will hear the SFE start to pump CO2. Allow the
system to equilibrate back to 240 bar. Then open the outlet valve, and again, allow the system
to equilibrate back to 240 bar. Once equilibrated, open the micrometer valve until you hear a
steady stream of CO2 coming out. Adjust the valve as needed.
10. Purge the cleaning pump by pressing the purge button once, open up the purge valve (small
white knob on the front of the cleaning pump) and then press purge again. When you see a
steady flow of methanol coming out of the purge valve, close the valve and stop the purging
process. Make sure the pump is set to 0.5 mL/min.
11. Turn on the cleaning pump and allow cleaning pump to run for 15 minutes to clean. After the
cleaning process, turn off the cleaning pump.
Experimental Procedure
1. Follow the same procedures for the cleaning process, except the pressure will be set to 300 bar
rather than 240.
2. You will then prepare the vessel by packing glass wool in one end, placing your weighed sample
into the vessel, then packing the other end with glass wool.
3. Run the sample for 30 minutes, make sure to use a weighed Erlenmeyer (or beaker) with
parafilm on the top to collect the sample.
4. When the sample is complete, close the outlet valve. (once the outlet valve is closed there is no
need to do anything with the micrometer valve).
5. Close the inlet valve. Once closed, open the vent valve to release the stored pressure in the
vessel. Once depressurized, remove the vessel from the oven (use gloves, it will be hot).
6. Open the vessel and the sample can be placed in the trash (for the wax extraction).
7. After running the samples, determine what the weight percent of wax in each sample is.
Sample Preparation
 Use about 1 g of sample
 When running the known sample, make sure the known percentage of wax is written down
Shut Down
1. Clean the SFE following the procedure outlined above.
2. Once clean, close all the valves.
3. Lessen the pressure to 50-60 bar using the knob.
4. Use the vent valve to release pressurized CO2.
5. Open the inlet valve to relieve internal pressure.
Trouble Shooting
 If the SFE is continually pumping while the system in equilibrating, open the oven to check for
leaks. If there is a leak, make sure to relieve the pressure using the vent valve before trying to
tighten the valves on the vessel.
 If the SFE is continually pumping and there are no leaks in the system, the CO2 tank may be
running empty.
Day 1:
1. Learn the properties of the SFE by cleaning the lines using the pump and methanol.
2. Run a preliminary extraction of solo wax (you will need at least three good runs)
Day 2:
1. Determine the efficiency from the extractions of the solo wax
2. Run at least three extractions (two known percentages and one unknown)
Data:
Sample
Solo Wax
Unknown
Before
1.0746 g
1.009 g
After
0.6753 g
0.1563 g
% Wax
62.84%
15.49%
Calculations:
Erlenmeyer flask=87.2415g
Wax before running= 1.0746g
Extracted wax= 87.9168g
Extracted wax= 87.9168g-87.2415g= 0.6753g
% yield=
% yield=
𝑚𝑎𝑠𝑠 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑
𝑚𝑎𝑠𝑠 𝑠𝑡𝑎𝑟𝑡𝑒𝑑 𝑤𝑖𝑡ℎ
0.6753𝑔
1.0746 𝑔
× 100%
× 100%
% yield= 62.84%
Erlenmeyer flask=74.0738
Wax before running= 1.009g
Extracted wax= 74.2301g
Extracted wax= 74.2301g-74.0738g= 0.1563g
% yield=
% yield=
𝑚𝑎𝑠𝑠 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑
𝑚𝑎𝑠𝑠 𝑠𝑡𝑎𝑟𝑡𝑒𝑑 𝑤𝑖𝑡ℎ
0.1563 𝑔
1.009 𝑔
× 100%
× 100%
% yield= 62.84%
Conclusions:
Using the SFE was difficult because the instrument was temperamental with leaks needed to be
resealed every time we ran a sample. It was also time consuming in that we had to clean the system
before running the actual experiment, and then clean the system again when we were finished running
the sample. Therefore, adjusting the instrument to prevent leaks and cleaning the system took up most
of our time when trying to operate this instrument. We found that the leaks were a problem because
the O-ring that sits within the column was destroyed and therefore there was nothing to seal the system
when you tightened the lid. After finding a new O-ring we were able to reduce the time spent on fixing
leaks. But because of time constraints we were not able to obtain 3 good runs of the standards.
Understanding how to operate the SFE was definitely learned during this lab since we had to deal with
all kinds of abnormalities and difficult situations. The purpose of this laboratory was to extract wax from
the wax paper through supercritical fluid extraction. From the samples we chose, the solo wax yielded a
63% extraction and the unknown yielded a 15% extraction. From these results we can see that we did
not get the best results which could have been due to the difficulties with the pressure of the column.
Overall, this instrument was more difficult for us to operate than others, but we gained a great deal of
knowledge from having to go through many troubleshootings.
Questions:
1. Supercritical CO2 extraction efficiency increases with density because solubility increases with
density and pressure. Since supercritical fluids (SCF) have a relatively high liquid-like density
their solubility is higher. This allows for high mass transfer rates between a solute and SCF. Also
fluids in their supercritical states have a high rate of absorption because their density is higher
as well.
2. The effect of temperature with supercritical CO2 is that is as well plays a factor in the solubility.
As temperature increases solubility increases allowing for a higher rate of absorption. Extraction
rates also increase at higher temperatures due to the increased value of the partition
coefficient.