Sunday, May 25, 2008

Vacuum Control - updated!

It took 88 cardboard boxes and 1.5 km of packing tape to get my belongings packed up and on its way in a container destined for Denmark. Hopefully, I'll see it all at the other end in 2 months time. So with that stage of the move over and done I believe it's time for a post.

Rotary evaporators are great and we use them all the time but solvents have a bad tendency to bump and splash resulting in a mess. One way to partly control the mess is the use of a splash guard but it is still a pain. Chemists in industry generally don't have these bumping issues because they can afford a vacuum controller. These are great little gadgets where you punch the vacuum you would like to achieve in and hit go. On the more fancy systems even this is unnecessary as a clever little vapour pressure sensing device regulates the pressure ensuring the perfect distillation. However, these things are expensive and high maintenance so universities don't normally have them. Recently, a good friend that works at one of Australia's top institutions introduced me to a simple piece of glassware that essentially replaces the fancy vacuum controller at a very low cost (see picture left). The principle is very simple. The tap has two setting one allows passage through a wide glass tube and the other through a capillary tube. When you start the rotary evaporator you have the wide tube open and when the distillation starts you switch to the capillary tube. The capillary tube basically ensures that the current vacuum is maintained and stops it from going further down. Too easy! In addition the solvent recovery is dramatically improve saving the planet and importantly also your pump. All specifications for the gadget can be found in this paper:
Prevent the Loss of Volatile Solvents in Rotary Evaporators with a Simple Device, Daan van Leusen, Journal of Chemical Education, 1994, 71 (1), pp. 54-55. D!
One of the regular readers just emailed me a picture with a similar set-up to mine that does the same trick (See comments and picture right). The main difference is that this alternative set-up doesn't allow you to turn the vacuum off by turning the tap. Were I work we have a house vacuum system that requires a lot of tap turning so the set-up above is nice as this simplifies turning the vacuum off. However, if you are using a diaphragm pump this alternative is perfect and presumably also significantly cheaper to produce. D!

Friday, May 02, 2008

The Robots are Coming

Posting on Curly Arrow is already a very erratic affair and things will not be improving for a while. There is less than two months til the big move back to Denmark. I'm experiencing total organisational chaos and trying desperately to obtain some results in the lab before it is too late. So please be patient.
I'm sure that the following paper from Journal of Medicinal Chemistry is great (I haven't read it). The title is certainly great.
Designing Active Template Molecules by Combining Computational De Novo Design and Human Chemist's Expertise
Eric-Wubbo Lameijer, Reynier A. Tromp, Ronald F. Spanjersberg, Johannes Brussee, and Adriaan P. IJzerman
J. Med. Chem., 2007, 50, 1925-1932