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Unformatted text preview: It is not always possible to quantitatively
remove the solute using a single
Your options typically are to:
Increase the volume of the extracting
solvent - not usually a good idea.
Use multiple extractions. Total amounts extracted are the sum of all
(p + pq + pq2 ... + pqn-1)C0V2 = (1-qn)C0V2 In our earlier example, 75% of a solute was
removed with one extraction. We can
determine how much would be removed from
10 sequential extractions.
q 1 - qn = E , A precursor to chromatography.
Multiple extractions can effectively remove a
single species or a group of related species at
the same time. ~
= 1 - 0.2510 = 1 - 9.6 x 10-7 %E %E = 100 (1-qn) = 0.25 E or = 10 = 99.9999% We can conduct a sequence of extractions to
effect quantitative separation of multiple
solutes - countercurrent extraction What do you do if the goal is to separate two or
more species with similar Dc values?
Even if the Dc values for two species differ by
1000, you still can’t get better than 97% purity. n= 0 1 2 3 We transfer
phase to the next
tube and add
fresh phase to
the first. ...
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This note was uploaded on 01/07/2012 for the course CHEM 290 taught by Professor Harvey during the Fall '08 term at SUNY Stony Brook.
- Fall '08