I voted this morning (don't forget to vote!); what should have taken 2 minutes to confirm my identity, sign the signature page, etc took a lot longer. I walked in about 30 seconds after the polls opened, but it was quite clear that they hadn't gotten their system worked out yet -- sigh.
While academia is not really known for efficiency, I think that performing research in chemistry is one of many different ways to learn how to work quickly and effectively. You have a column to run, fractions to TLC and product to isolate; if you do this haphazardly, it will take 2 hours. If you do this efficiently, it will take 45 minutes. Which do you think is a better use of your time? I've also found that setting up a system to quickly perform a task is a great way of achieving some sense of "flow" and enjoying one's self in the lab.
Of course, not all of chemistry is about 'increasing sample throughput' or turning yourself into a robot; sometimes, it's about taking 2 hours to carefully stare down all your data. But if you've got a task to do, you might as well get a system in place and just do it. Here's to taking care of business in the lab, and here's hoping those poll workers get their system in place before noon.
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You can finish a column in 45 minutes? You're hired, I got two waiting for you right now!
ReplyDeleteWC Still's original paper on flash chromatography says 10 g of material can be separated in 10 minutes. Insert laughter here. Haha.
ReplyDeleteJOC; 2923, 43, 1978.
Yeah, that Still paper just cracks me up. It makes it sound sooooo damn fast!
ReplyDeleteThis, on the other hand, 10g in 15 minutes is totally do-able (assuming you have generous Rf diffs)
http://curlyarrow.blogspot.com/2008/01/dry-column-vacuum-chromatography-dcvc.html
E-s, have you actually used that method? I showed it to my boss a while ago and downloaded the paper, but we're still not sure how generally user friendly it is.
ReplyDeleteYes, regularly. I use it for anything over ~ 5g. Just like flash columns, the first 3-4 times will be a cluster*, but after that it's worth it. If you have a glassblower, it's nice get an adaptor like chembark's, as it saves you having to disconnect the tubing for each fraction.
ReplyDeleteImpt details: make sure you have the right size silica! I also add a layer of sand on top, and then a filter paper, so pouring new solvent doesn't make channels. My method: pull 2 fractions with pure hex or pet ether, then increase each one by 5% of whatever your polar solvent is.
IMHO, it is most worthwhile if you have a big scale reaction with lots of by-product crap (Mitsunobu, HWE, etc) : just rotovap down the whole mess crude, load the oil/sludge, and off you go.
Very often you can purify 15-20g fast, and get it pure enough to recrystallize and be done with the the whole sheebang in a morning. It saves lots of solvent too.
(oops, "chembark's" above should be "curlyarrow's")
ReplyDeleteAlso, I should have made it more clear: you *can* get separations that are just as good as normal flashing, and it works great for 2-4g, I just don't tend to use it for either of those situations.
The Aldrich ChimActa article is also quite good.
The dry column take does work well, in my experience. Used to use it to separate 10-20g of oligo-saccharides after a few flubbed attempts.
ReplyDeleteAlso nice in that didn't need to watch it as closely as a flash column (which would be more fun had I had a trained monkey to collect fractions and refresh solvent resevoir...)
groan. I spent four hours purifying 12 g of a pyridyl quinoxaline derivative using FC. It took around 3 L of MeOH-EtOAc. Wish I had the bucks for one of those DCVC-setups. At least the separation was good :-)
ReplyDeleteYou don't need the fancy setup! Just use a frit! The correct silica is the only thing you need to scrounge, beg, borrow or steal. All the rest is just gravy.
ReplyDelete