Most of the papers and journals i read were preferably using ethanol as co-solvent for their SFE extraction of polar compounds. probably because ethanol is a food-grade chemical. i just want to know is it the used of methanol as co solvent will affected the pharmaceutical quality of the compunds? Methanol have low boiling point compared to ethanol. Thus i planned to used methanol instead of ethanol so the temperature for SFE-CO2 extraction will be lower. Most of the extraction done by using ethanol as co-solvent will have boiling point almost like conventional soxhlet extraction where im afraid for the decomposition or disturbance for thermo labile bioactive compounds.
Methanol can be used and several papers have reported this, and it is possible that methanol may discharge alonwith CO2
I think you puvez used methanol, researchers genergalement use ethanol because it is not toxic. but, methanol is more polar than ethanol, therefore it is very used to extract the antioxidant molecules.
A s compare to any other Methanol is highly polar and best solvent for extract bioactive compounds from food materials as well as other plant samples.
Methanol is the third most popular SFE co-solvent (after ethanol and water). Its excellent solvent properties are often overshadowed by toxicity (especially in food applications) and ethanol is used instead.
It appears that your biggest concern is thermostability of the bioactive compunds during removal of the solvent. I think that good solution may be using the vacuum evaporation - it will allow you to remove the solvent (ethanol or methanol) at 30°C.
I enclose the link to the guide created by one of equipment manufacturers. I hope you can find there some helpful data.
http://www.buchi.com/sites/default/files/Application_Guide_Multivapor_1205_komplett.pdf
yes, you can , but be careful with methanol concentration. Higher concentration moves the critical point of mixture CO2-methanol and you can extract at sub-critical instead supercritical conditions.
The problem is that ethanol residues do not matter but methanol residues may not be acceptable. You should take into account the economy of the whole process. Vacuum evaporation is a good idea, the only problem may be the existence of an azeotrop. Both alcohols form azeotrops with many polar compounds and it also depends on temperature/presssure, you have to check it. Of course, the mixture critical point always differ from the critical points of pure components, there are several types of dependences as described by Van Konynenburg and Scott. It does not matter much whether the extraction process is subcritical or supercritical, in fact subcritical extraction is also used. What is important is the density, viscosity and polarity of the solvent. There is not a big difference if you are close to the critical point.
thanks guys for the answer..it really helps me a lot. so i'll use ethanol for supercritical. hope it wont become a problem to compare soxhlet and supercritical using different solvent
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