Rob Harvey
Lab 7 SFE
Introduction:
Supercritical fluid extraction (SFE) is a method for removing an analyte from some type
of matrix. Older methods dealing with just organics were tedious, and created toxic byproducts.
SFE could be a way to do these extractions safely. Also it can be used for many other types of
analytes, it’s not just restricted towards organics. CO2 is the supercritical fluid that is most
commonly used, and is what is used in our lab. A supercritical fluid is one that is above it’s
critical temperature, and pressure. The only downside to CO2 is that it is somewhat non-polar,
which means polar analytes would not be extracted as well. The SFE instrument can also be
modified in a way that would allow for supercritical fluid chromatography (SFC), which is a
very efficient separation method. It has the advantage of LC where the analyte does not have to
be volatile, and the advantage of GC of being able to use capillary columns.
Purpose:
The purpose of this lab is to learn how to operate the SFE, and extract wax from paper
that was manufactured to wrap food. By working through this lab, we are able to send
information to Glatfelter about the possible use of this technique in their lab.
Procedure:
Day One
1. Learn the properties of the SFE by cleaning the lines using the pump and
methanol.
2. Run a preliminary test on solo wax.
Two runs were able to be done of the solo wax for the first day.
Day Two
1. Determine efficiency of solo wax extraction.
2. Run three more extractions, two knowns and one unknown.
Note: Due to time constraints one two runs were done, one with Sample 4,
and one with Unknown A.
Note on what to mass:
1. Mass of the empty flask (put parafilm on first)
2. Mass of sample (either solo wax or paper)
3. Mass of both extracted wax and flask.
4. Mass of remaining paper (for samples and unknown)
5. You can get mass of extracted wax by subtracting the mass of both from mass
of the flask.
Results:
Solo Wax Run 1:
Mass of Flask: 77.2496 g
Mass of Sample: 1.0158 g
Mass of Both: 78.1504
Mass of Extracted Sample: 0.9008 g
Percent Recovery*: 88.7%
Solo Wax Run 2:
Mass of Flask: 82.3679 g
Mass of Sample: 1.0108 g
Mass of Both: 83.2208 g
Mass of Extracted Sample: 0.8529
Percent Recovery: 84.4%
*Percent recovery was obtained by dividing the extracted weight of wax by the original weight
of the wax.
Sample 4 16.4% Wax
Mass of Flask: 77.2419 g
Mass of Paper: .9293 g
Mass of Both: 77.3530 g
Mass of Extracted Wax: .1111 g
Mass of Paper Left: .7896
Calculated % Wax*: 12.0%
Percent Error**: 2.68%
Unknown A
Mass of Flask: 83.8341 g
Mass of Paper: .5945 g
Mass of Both: 84.0010 g
Mass of Extracted Wax: 0.1669 g
Mass of Paper Left: 0.5156 g
Calculated % Wax: 28.1%
*% Wax calculated by dividing the mass of extracted wax by the original weight of the paper
**Percent Error calculated by taking the absolute value of actual % Wax – calculated % Wax,
then dividing by the actual % Wax
Conclusion:
Overall this lab went well. The SFE, although seemly intimidating, is a very easy and
straightforward instrument to use. While operating the instrument we never had any major
issues, the only issue we had the first day was to make sure the screws were tightened that
plugged into the extraction tube. There were several times that the tube leaked, but soon we got
familiar with if it was tightened the whole way. When running our two solo cup runs, we forgot
to weight the flask with the parafilm on it, so some of the wax sample was lost. We remembered
to do this for Sample 4 and Unknown A however. Another thing that we noticed was that due to
the high pressure, the parafilm hole around the needle expands, and some wax escapes. For our
lab is did not have a major effect, but this could possibly be an issue that should be addressed if
this became part of an industrial process. When we ran Sample 4, not all the wax was extracted.
I think that this wax was still in the tubes, and this led to the high %Wax we calculated for our
Unknown. In our limited time lab, the 30 minute runs are enough, but again if this becomes an
industrial technique, I believe they should run their samples for more than 30 minutes. When we
cleaned it at the end of the day, wax was stilling coming out, which also shows some wax was
still in the tubes. In conclusion the lab went very well, and was very straightforward, the only
issue was the slight percent errors we had.