I'm a graduate student in a marine natural products lab doing isolation and structure elucidation. We currently rotovap our extracts to concentrate them with a water bath temperature of 25 C, regardless of solvent. This makes pulling off water rather difficult. I was curious if anyone in a natural products lab has noticed if raising the temperature negatively affects the compounds in your extract. As a discovery lab, I don't want to change the compounds from the organisms before I can elucidate them. Thanks for your guidance!
Dear Kristin, here are a couple of thoughts.
- Any possibility of changing your vacuum power? Rate of evaporation will increase exponentially with decreasing pressure.
- Try Azeotrope. If you add a certain amount of an organic solvent (e.g. ethanol or benzene) to your extract, they form an azeotrope which evaporates at a lower temperarture (both solvents evaporate). You can easily find Azeotrope tables for water and pick a solvent which best suits your purpose.
- Try changing rpm of rotavap, in rotavap, evaporation takes place from liquid film formed on glass, changing the thickness of the film (reducing it) will increase evaporation rate.
- Lastly you've got to remember that your extract temperature in the flask could be a little lower than that indicated for the water bath (specially for stronger vacuums). If you know this difference it will give you peace of mind and you can possibly increase your water bath temperature by a couple of degrees.
Hello Kristin,
We believe that the temperatures and vacuum pressures could be adjusted accordingly with the solvents required to be evaporated.
Inclined temperatures and rotation speeds would obviously support faster evaporation. But, temperature raise would affect negatively on the compounds of interest depending on their stability.
If the water content is higher (eg. 50-70% EtOH, MeOH extracts), you could also try evaporate the organic solvent first (completely) and move to freeze drying to remove the remaining water.
Hi Kristin,
I do not know if you mean marine plants or marine animals. Basically, for plant compounds, if there is a vacuum, the temperature can be raised up to 35 degrees Celsius. Be aware that higher temperatures may damage your composition. Adding any other compound or solvent may also affect the structure of the material.
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