From our friend Neal Anderson and his book:
Understand the partitioning of the desired product in each phase during every stage of the extraction process. Collect each "spent" phase, label the container, and store until it is clear that the extract can be discarded without losing yield or valuable process history that could be collected by analyzing the extract.You know, this is pretty good advice, especially during that first large-scale extraction. At the same time, it can start to clutter up the lab if there's a bunch of work going on. Nonetheless, good advice. (P.S. That "label the container" part is really important, too.)
What, you mean labeling the flask 'Aq 1' isn't specific enough?
ReplyDeleteif you had followed your reaction progress by HPLC, you know where your product goes (and the impurities). So if you deal with products where one would expect aqueous solubility it does not hrt to put one extra vial on HPLC, with the combined aq. phases.
ReplyDeleteAs always, before you scale up, do a pilot experiment where factors like the best conditions for extraction can be worked out.
@milkshake - I'd like to point out that not EVERYTHING is HPLC sureproof....I'm working with a bunch of small-ring amines with no chromophore....and ELSD just shows me a bunch of noise....NMR for the win! (and yes, oftentimes I see some in the water)
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