I am using solvents like 2-ethoxyethanol, DMF or toluene at times for synthesis and since they are all high boiling point solvents, it is very very difficult to evaporate them in a rotary evaporator.
To evaporate these without boiling at high temperature, and to have the added benefit of boiling at low temperature, you will need a good vacuum source that is solvent resistant, a good high power low temperature cold trap, that is also solvent resistant, and a leak tight system. A rota-vap is solvent resistant, not leak tight, doesn't have a low temp cold trap but you can buy a good pump.
If you have money to spend, lots of it, then a solvent resistant centrifugal evaporator from Genevac will do what you need, reliably and repeatably. You do have to have deep pockets to get all this in one machine as they are developed for the rigors of the pharmaceutical industry.
Otherwise, use a higher temperature in the rotavap, see if you can tighten up the joints (parafilm not vac grease - this ends up in the product!), improve coolant to the cold trap if you can, try and beg a dry ice / acetone trap, likewise can you get a pump.
Good luck.
Rob
Just simply reducing the pressure, you will find the boiling point have decreased for solvent.Solvents with higher boiling points such as water (100 °C at standard atmospheric pressure, 760 torr or 1 bar), dimethylformamide (DMF, 153 °C at the same), or dimethyl sulfoxide (DMSO, 189 °C at the same), can also be evaporated if the unit's vacuum system is capable of sufficiently low pressure. (For instance, both DMF and DMSO will boil below 50 °C if the vacuum is reduced from 760 torr to 5 torr [from 1 bar to 6.6 mbar]) However, more recent developments are often applied in these cases (e.g., evaporation while centrifuging or vortexing at high speeds). Rotary evaporation for high boiling hydrogen bond-forming solvents such as water is often a last recourse, as other evaporation methods or freeze-drying (lyophilization) are available. This is partly due to the fact that in such solvents, the tendency to "bump" is accentuated. The modern centrifugal evaporation technologies are particularly useful when one has many samples to do in parallel, as in medium- to high-throughput synthesis now expanding in industry and academia.
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