Leben
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Steam Distillation vs Sohxlet Extraction... difference in nature of compounds recovered?
I'm thinking of going after some essential oils in various herbs, spices, vegetables, and so on.
I've seen some Sohxlet extractions done where after evaporating the solvent, most of what was left was solids that had been extracted from the plant
matter (depends on circumstance). Where as steam distillation always seems to yield an organic type oil.
Is steam distillation going to target more the already liquid components of a substance, whereas sohxlet is geared more towards extracting the solids
that won't come out via steam distillation? Is this too great of a generalization?
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UnintentionalChaos
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Steam distillation will remove the volatile organic components from plant matter. Soxhlet extraction will remove these in addition to lipids, waxes,
carotenoids, etc. Anything organic-soluble in the plant matter. The soxhlet extraction may give a truer fragrance relative to the original material
since it includes all the components in the plant, but they are often deeply colored and may be pasty or solid. CO2 extraction is the same way.
Materials produced this way include most floral scents such as jasmine and rose and things like oakmoss. They are called "absolutes" in the fragrance
industry. The bulking of the essential oil by waxes and lipids can be very beneficial since the volatile oil produced with steam distillation is
extremely strong, very expensive, and difficult to measure.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Little_Ghost_again
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Also some times the hydrosol (liquid bit that collects) can go moldy, so I keep mine separate from the distillate itself. I like Soxhlet and I tend to
extract then distill so far and try and salt out or do whatever to get the part I want (I am still messing with this as I am a complete noob)
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Chemosynthesis
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I have heard some speculate that yields of thermally sensitive compounds may be reduced in a Soxhlet if in contact with the heated reservoir glass. I
guess it's possible, but I consider the source a bit eccentric. They refuse to use chromatography columns in lieu of repeated recrystallizations at
the hands of their slave labor.
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aga
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Pull a vacuum on the Soxhlet and reduce the BP of the solvent anyone ?
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Chemosynthesis
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^ Good suggestion. That would definitely be an option. I am not sure exactly what he does as he basically never publishes anymore, nor even seems to
have any funding, but if you measured the temp of the glass to ensure you were below degradation temps, that does sound much more reasonable. Then
again, as annoying as I find, say gravity chromatography rather than flash or pressurized... I would take that over days or recrystallizations too. I
have heard also frowns upon using anything other than latent enthalpy to evaporate the solvents. Yes, if you are wondering, he looks to be about a
million years old.
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aga
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Not sure that the Syphon will work under vacuum.
Seem to recall something about atmospheric pressure coming into it somewhere.
I'll try it and find out.
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