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Rotary evaporators

Gray Wolf

A Posse ad Esse. From Possibility to realization.
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Rotary evaporators are one of the ways that fractional components can be distilled out of a solvent mixture, while minimizing heat input. In is simplest form, rotary evaporation is a boiling flask of solution is rotated on its side in a hot bath, while under vacuum, with the vapors being condensed and collected using a chilled heat exchanger.

The rotation coats the inside of the boiling flask with a thin film, greatly enhancing film surface area and evaporation rates. Using vacuum instead of heat also allows fractionally distilling fragile substances sensitive to heat, such as carboxylic acids.

By controlling the heat and vacuum level, individual fractions may be distilled off and collected at their different boiling points.

There is more than one company manufacturing lab size rotary evaporators, and the cheapest is not inexpensive, sooo we’uns decided to attempt a comparison of available offerings, to share with ya’ll.

Not just what is available, and what does it cost, but what is the utility at the margin, aka bang for the buck, because they also range in price.

One out of three success from our first round of importuning central suppliers for the loan of a test unit for impartial-pari-passu (IPP) (even, same/same, side by side) comparison with their competition, to share with our readership.

Hee, hee, hee, snicker, snark, snort, I’m pleased to report that Heidolph is proud and confident enough of their Hei-VAP Precision ML G3, to supply it and a chiller for our trials and sooooo, we’uns have been having our way with her at the Pharm.

She is a gaugus piece of precision equipment from zee fatherland, who gets extra points for being purdy to gaze longingly upon, but more importantly, she has been reliable and a joy to operate. A admirable quality that lingers in mah heart, after the honeymoon is over and the joy of her good looks wanes!!

More fractional distillation experiments underway, but check out Jules report on ethanol removal using the Heidolph Hei-VAP Precision ML G3 at:

http://skunkpharmresearch.com/evaluation-of-heidolph-instruments-hei-vap-precision-ml-g3/


Thank you Jules from Specialized Formulation’s for conducting the tests, as well as Rick from Botanical Analytics for lab space, and support.

Thank you Heidolph for sharing the ML G3’s charms with us’ns and readership! We admire manufacturers who are confident enough in their equipment to belly up to the bar for unbiased IPP comparison

We also still have offers out to other manufacturers, and if any more decide to join us at the bar to strut their stuff, we will share that as well.

Lu lu lu lu lu lu lu lu lu lu lu, let the fun begin!!
 
BHOgart only distributed five 10L rotavaps in CA, I snagged one of them. Seems to be pieced together from various Asian manufacturers. The manual was written by someone with ZERO understanding of the English language. Yet, the performance is on point.

We have switched to using a AI 22 cfm dry scroll pump in conjunction with an AI T40 cold trap, as this setup will also work with the new 50L rotavap from AI which is still definitely on my wish list.
 

HG23

Member
Why did you choose the dry scroll pump over a sliding vane if you need to get the cold trap either way?

Also, I have been shopping for 10L rotavaps on alibaba and it seems like a complete unit with chiller and water aspirator style vacuum pump is around 5-6k.
 
Why did you choose the dry scroll pump over a sliding vane if you need to get the cold trap either way?

Also, I have been shopping for 10L rotavaps on alibaba and it seems like a complete unit with chiller and water aspirator style vacuum pump is around 5-6k.

The cold trap is both a $2700 "insurance policy" for the vac pump, and its very necessary for terpene collection

BHOgart definitely charges a premium, close to 8k out the door just for the rotavap, no vac pump or circulating chiller
 
Also, when I'm recovering ethanol I use the cold trap in front of a Welch chemical duty pump, because you can't use the dry scroll pump with ethanol vapors.
 

G.O. Joe

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A few maybe most labs mate rotavaps with diaphragm pumps. The vacuum isn't high and solvent vapor is OK.
 

fishb0wl

New member
What is the proper vacuum tubing to be using, Does anyone have any sources? I am looking for PTFE tubing or something I can use for terpene isolation, something that won't leach nasties.
 

HortiLab

Active member
Very interesting topic Gray Wolf. Curious at what temp do you run the chiller for best results? I take it as cold as possible?
 

Gray Wolf

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Very interesting topic Gray Wolf. Curious at what temp do you run the chiller for best results? I take it as cold as possible?

Good question! I run it at -20C, but Jules used 0C for this experiment.
 
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