I am using acetone and heptane for separate soxhlet extractions, then evaporate the solvent under vacuum. However, once evaporation is complete I can still detect the solvent smell, so it is affecting my crude yield. Thanks.
There are several related threads on soxhlet extraction, please check these:
Hi B. R. Rajeswara Rao,
Thanks for your reply.
I already did some research here in the questions section to see if someone else encountered my problem. What I meant is, when evaporating the solvent under vacuum, to precipitate the plant extract, how can you be sure that all of the solvent is removed? And also, how can you be sure that the essential oils do not escape in the rota vap?
Thanks!
In case you are extracting essential oil from your plant biomass for phytochemical studies or for its biological activities, an alternative method is to hydro-distil the biomass in Clevenger trap where there is no need to use any solvent.
As far as your present sample is concerned if you run GC-FID of the sample you can see a solvent peak if any solvent is left in the sample. Concerning loss of essential oil, it is likely that some early boiling compounds may be lost depending on the composition of your sample and conditions of rotavapor.
We extracted essential oils from hydrosols or distillation waters of different cultivated aromatic crops employing hexane as the solvent. The solvent was separated by vacuum distillation in rotavapor. The initial amount of solvent used was more than the solvent recovered, that is we noticed loss of the solvent in the process.
For the removal of the solvent, first remove the organic solvent as much as possible using rota-evaporator. then suspend the extract in the small quantity of distilled water and then subject to the freeze drying..... however, in this case, the product extract will be highly hygroscopic. so must be protected by keeping in tightly closed container.
Thanks a lot for your answers/replies!
I am testing different techniques, including: soxhlet with acetone and heptane, hydrodistillation, and scCO2 (collect the extract in DCM).
The positive result about this is that till now the solvent does not appear in the GC-FID or GC-MS chromatograms, meaning that the residual solvent is not present.
I have never tried freeze drying, so will suggest it as an alternative to my supervisor.
Thankyou!
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