Supercritical Fluid Extraction
Introduction:
Supercritical Fluid Extraction (SFE) is used to target a specific product from a matrix. It can be
used for solids and liquids. CO2 is used as the mobile phase is SFE. SFE is useful because of its
speed, ability to extract from solids and liquids, the solvent strength can be changed by pressure
and temperature, and most supercritical fluids are cheap, inert, and non-toxic. Supercritical fluids
are different from other liquids because they are above its critical temperature and pressure,
making it have similar characteristics of gases and liquids.
Purpose:
The purpose of this lab is to be able to operate the SFE correctly and be able to extract samples
using the SFE.
Method:
Day One
1) Setup SFE and clean the lines before imputing the sample
2) Run a preliminary extraction of solo wax. Run three times
3) Determine the efficiency of the extractions
Day Two
1) Setup SFE as before.
2) Run three extractions. These will be two known extractions and one unknown.
3) Determine the efficiency of the extractions.
Results:
Wax Samples
Wax Sample 1
Wax Sample 2
Wax Sample 3
Wax Mass
1.0029
1.0008
1.0020
Erlenmeyer Flask
63.0519
82.2998
73.8616
63.916
83.1785
74.6487
Percent Recovery
86.2%
87.8%
78.6%
Percent Difference
13.8%
12.2%
21.4%
Mass
Erlenmeyer Flask
Mass and Sample
Paper Samples
Paper Sample 1
Paper Sample 2
Paper Sample 3
(7.87% wax)
(13.5% wax)
(unknown)
Paper Sample Mass
1.0019g
1.0004g
1.0030g
Erlenmeyer Flask
73.8616g
82.2998g
63.0530g
73.965g
82.4115g
63.1314g
Percent Recovery
10.3%
11.1%
7.8%
Percent Difference
89.7%
88.9%
92.2%
Mass
Erlenmeyer Flask
Mass and Sample
Calcultaions:
Percent Recovery=
Mass of wax recovered
x
Actual mass of wax
100%
Wax Samples:
#1.
(.8641/1.0029) * 100%= 86.2%
#2.
(.8787/ 1.0008) * 100%=87.8%
#3.
(.7871/1.0020) * 100%=78.6%
Paper Samples:
#1.
(.1034/1.0019) * 100%=10.3%
#2.
(.1117/1.0004) * 100%=11.1%
#3.
(.0784/1.0030) * 100%=7.8%
Percent Difference =
Known amount of wax−amount of wax recovered
x
known amount of wax
100%
Wax Samples:
#1.
(1.0029-.8641/1.0029) * 100%=13.8%
#2.
(1.0008-.8787/1.0008) * 100%=12.2%
#3.
(1.0020-.7871/1.0020) * 100%=21.4%
Paper Samples:
#1.
(1.0019-.1034/1.0019) * 100%=89.7%
#2.
(1.0004-.1117/1.0004) * 100%=88.9%%
#3.
(1.0030-.0784/1.0030) * 100%=92.2%
Conclusion:
In conclusion, the SFE is a very useful machine for extracting many different types of substances
to allow for further analysis. The machine provides a fast effective way to examine samples, but
when using it for my group, our percent recovery numbers were very low for the paper wax
samples, which were close to their percent wax values, but we did receive good results for the
wax samples for the most part and recovered most of the sample. Reasons for varying results
could be the wax percentages were not correct, human error, or some of the wax was stuck in the
releasing tube. The SFE was easy to use after using it for a few times and becoming familiar with
how it works. Cleaning the machine is very important for the success of the extraction.
Questions:
1. Why does extraction efficiency of supercritical CO2 increase with density?
Extraction efficiency increases with density because extraction at higher pressures will favor
more polar and higher molecular weight analytes. When the pressure is increased so is the
density.
2. What is the effect of temperature and why?
As the temperature increases the solubility parameter decreases, which means it is less likely to
become soluble and therefore decreasing the extraction efficiency.