23_Extraction-page4

23_Extraction-page4 - It is not always possible to...

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Unformatted text preview: It is not always possible to quantitatively remove the solute using a single extraction. 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 extractions so: (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. n 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 the extracting 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.

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