When I was in grad school, I tested out some new-fangled separatory funnel idea that some small company was trying to launch. I can't locate a picture of one of the things, but it had a sort of piston/reservoir arrangement at the bottom, which let you draw the lower layer down and pour off the upper one. I tried it out some, and didn't find it any more convenient or effective than the good ol' standard model.
Even if it had been, so what? How much better could it have been? I'm not sure how much improvement there is to be had in the classic sep funnel design. Those things haven't been around for a century or two for nothing. What led this inventor to think that the world was waiting for him to fix this nonexistent problem, I don't know. And that's something that everyone who's trying to invent something needs to keep in mind: even if your brainchild works, will anyone want it?
I think that some innovative types miss this in their drive to get all the kinks out of their latest invention. It's easy to misdirect this sort of energy, particularly when all that hard work can be employed to keep you from dwelling on such disturbing questions. I'm not suggesting that people sell themselves and their ideas short - just that they think them through as much as they can. If you're not attacking a real problem, it's likely that no one is going to be interested.
If someone tried to sell me on a wonderful new gizmo to, say, spot my TLC plates for me, I don't think I'd be jumping up and down to try it out. A glass capillary, home-made or store-bought, works just fine, and I rarely have any cause to complain. And besides, it only takes a second or two. How much time and irritation could a new device save? On the other hand, I would be very interested in a fivefold-faster rota-vap, should some bright person figure out how to make one. Moving up the scale, if you have something that will allow me to predict (really predict) oral absorption for a new drug candidate, then you can name your own price.
But no one's offering me either one of those, as far as I know. So in the interim, remember: not everything new is improved, and not everything is improved enough to be worthwhile.
1. GC on July 7, 2006 10:54 AM writes...
Diffusion pump and a bucketload of boiling chips or sieves. Nobody ever believes me on this.
Permalink to Comment2. Don B. on July 7, 2006 10:57 AM writes...
I always thought that the biggest improvement to separatory funnels was replacing the ground glass joint at the exit end with a Teflon (TM) joint. It certainly cut down on leakage.
Permalink to Comment3. GC on July 7, 2006 11:08 AM writes...
Diffusion pump and a bucketload of boiling chips or sieves. Nobody ever believes me on this.
Permalink to Comment4. GC on July 7, 2006 11:08 AM writes...
Diffusion pump and a bucketload of boiling chips or sieves. Nobody ever believes me on this.
Permalink to Comment5. George Laszlo on July 7, 2006 4:53 PM writes...
Here is another real-world example of a problem that does not need fixing: inhaled insulin. You don't agree? Well, follow this link to find out why. http://laszloletter.typepad.com/the_laszlo_letter/2006/05/innovation_the_.html
Permalink to Comment6. GC on July 7, 2006 5:04 PM writes...
Diffusion pump and a bucketload of boiling chips or sieves. Nobody ever believes me on this.
Permalink to Comment7. anon on July 7, 2006 5:05 PM writes...
A colleague in grad school insisted upon doing his chromatography in sep funnels, claiming that he achieved better separation. I never have seen this since, though.
Permalink to Comment8. Milo on July 7, 2006 5:08 PM writes...
I have actually seen someone pack a sep funnel with silica for the purpose of chromatography. This person claimed that the conical shape somehow imporved the separation... I was never convinced myself...
For a fast rotovap, try cooling the trap to -78C. I find it works wonders.
Permalink to Comment9. Derek Lowe on July 7, 2006 5:09 PM writes...
I've never seen the sep-funnel chromatography trick, myself. I would think that the conical shape would actually make the bands wider as they went down. The amount of silica per vertical unit of column is decreasing, and the effect of the column wall is increasing. Maybe if you had a tube that gradually flared toward the bottom, with a sintered glass plug to hold the silica. . .anyway, if someone seems to have better separations this way, I'd guess that it's because they're using more silica gel than usual. We need a side-by-side test with some colored mixture. . .
As for the rota-vap, hey, my cold trap is already cooled by dry ice. But I want it even faster than it is!
Permalink to Comment10. Milo on July 7, 2006 5:10 PM writes...
Oh! Listen to Dr. Fancy-Pants industry guy with his cold rota-vap!
We in the Great White Tower, on occasion, have solid water to cool our rota-vap traps...well...when the ice machine works...
There is always LN2... (and the LO2 that condenses out)
Permalink to Comment11. Derek Lowe on July 7, 2006 5:11 PM writes...
Yep, and the thing is, the cold-water condensor models cost more than the dry-ice ones. Of course, you'll eat that initial savings pretty quickly paying for the dry ice. . .
Permalink to Comment12. secret milkshake on July 7, 2006 5:13 PM writes...
have you ever had the water coil in your rotavap condenser impoding under vacuum - and flooding the *entire* rotavap in matter of seconds? The sight is priceless.
Permalink to Comment13. Harry on July 7, 2006 5:13 PM writes...
Secret- can't say I have, but I did once see a fellow who had been feeding selenium dioxide solids down an allihn condenser into a 22 liter flask half full of refluxing toluene try to dislodge a clog with a glass rod.
You can guess what happened next.... fortunately there was no fire, but toluene fountained to the ceiling. It was a most ummm... enlightening experience
Permalink to Comment14. Chromatographer on July 10, 2006 4:59 PM writes...
Regarding the conical chromatography column, scientists in China have evaluated conical columns with various conical angles and their effect on preparative chromatography. They saw a 50-60% increase in sample loadability over a cylindrical column. Here's the references:
Permalink to CommentJournal of Chromatography A, 1033 (2004) 275-281 and 1108 (2006) 218-224.
15. VH-! on July 18, 2006 9:44 PM writes...
If your interested in a faster rotovap check out:
http://www.vapourtec.co.uk/home.php
I've used this thing and it does what it says it can do. We were able to take down H2O/ACN HPLC fractions (~12mL) in ~10 min at ~40C. Very impressive. Not sure how reliable it is.
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