DCHAS-L Archives, Jan 10, 2024 - Re: [DCHAS-L] [NAOSMM] Rotovap Vacuums and Condensers

Completely agree. Dry ice traps are the most common here. Cold water is just not sufficient to condense most organic solvents.

We generally discourage house vacuum systems for applications like this. The people using the vacuum are generally not responsible for maintaining the pumps, so there isn’t a large incentive for those users to use effective cold traps. Small diaphragm/membrane pumps at point of use work best, and even with good traps that exhaust can still have enough organic vapors to slowly damage the often used tygon tubing.

-Aaron

Aaron McCoy, PhD

Asst. Chemical Hygiene Officer

Environment, Health & Safety

University of Wisconsin-Madison

From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Craig Merlic
Sent: Tuesday, January 9, 2024 1:07 PM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: Re: [DCHAS-L] [NAOSMM] Rotovap Vacuums and Condensers

All,

Anyone using a rotovap should be using a condenser with dry ice or a recirculating chiller set to a low temperature.

Tap water is generally not cold enough for efficient condensation of low boiling solvents. Hence, if one uses a water aspirator the organic solvents end up going into the lab air and also down the drain. If one uses a mechanical pump they often produce lower pressures, so even more solvent can be blown out in to the lab air. Sometimes with mechanical pumps set to low pressures one even needs to use two dry ice condensers in series.

Craig A. Merlic

Professor of Chemistry, UCLA Department of Chemistry and Biochemistry

Executive Director, UC Center for Laboratory Safety

http://cls.ucla.edu

From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> on behalf of James Kaufman <jkaufman**At_Symbol_Here**LABSAFETYINSTITUTE.ORG>
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Date: Tuesday, January 9, 2024 at 8:18 AM
To: <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Subject: Re: [DCHAS-L] [NAOSMM] Rotovap Vacuums and Condensers

I recall when the town of Newburyport, MA put in water discharge restrictions that caused Strem Chemical Co to stop using a water aspirator and purchase a separate vacuum pump. They added a cold trap to the line.

Why don't you do an experiment and put a cold trap between your Rotovap and the house vacuum? ... Jim

PS. LSI now has virtual lab inspections, safety program evaluations, document reviews, plus courses and seminars ... all virtual. And, a complimentary, updated version of our classic Laboratory Safety Guidelines is now available on our website ... https://www.labsafety.org/product/lab-safety-rules

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On Mon, Jan 8, 2024 at 1:26 PM Jeremy B. Vanderhyde <jeremy.vanderhyde**At_Symbol_Here**mail.wlc.edu> wrote:

Hello, fellow NAOSMMites!

Our school has recently begun questioning the equipment and procedures we use when rotovap-ing in our organic labs. Currently, we evaporate off using the house vacuum and condense using a cold-water coil condenser that is just connected to the domestic cold-water supply. I would just like some feedback and input as to what some of you are using and why.

For context, our science building is about 20 years old, and for many years has had a history of causing many latex/rubber/elastic objects to deteriorate in a short amount of time and in weird ways (anyone else have melting cabinet bumpers?) Administration and facilities have done a few things to try to get to the bottom of what could be causing this, and the most recent thing they've hit on is that it could possibly be vapors from the rotovap leaking into the air somewhere that is contributing to this. Our one-and-only organic professor admitted that only a fraction of the solvents that are boiled off are actually condensed and recaptured by the current condensing setup, so administration asked facilities to verify that the house vacuum vents outside (and not just into the pump room) which they were able to do. Even with that information, they are pursuing the idea of purchasing a stand-alone vacuum to put in a hood to pull the vacuum for the rotovap. In my mind, this would be a less optimal solution than using the house vac, at least from the standpoint of trying to release as few solvents into the building air as possible.

We are also looking at solutions to increase condensation rates such as an electric water chiller, which I think does make sense, but I'm also interested in hearing what you use for that.

Thanks in advance for any input!

Jeremy

-----

Jeremy Vanderhyde

Science Laboratory Services &

Building Manager, Generac Hall

Wisconsin Lutheran College

8800 W. Bluemound Rd.

Milwaukee, WI 53226

Work: 414-443-8766

Cell: 414-885-7762

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