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Author Topic: determining the amount of extraction solvent to use?  (Read 107 times)

NeilPatrickHarris

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determining the amount of extraction solvent to use?
« on: December 23, 2009, 04:54:26 PM »
how would one go about calculating the amount of extraction solvent one should use and the different volumes between actual the extractions themselves?
how would the choice of the extraction solvent itself effect this, ie: the use of solvents with differing dielectric constants such as dcm vs toluene, etc (example: it may take 12 extractions with hexane to extract the same amount of desired compound that 3 extractions with dcm might do)?

i've seen many different amounts of extraction solvent used for a particular work-up and am curious to learn how to calculate it for myself and see what it should be.  i've read that the starting amount of compound that you wish to extract isn't really even a concern, but i'll admit i've read a couple pages on nernt's law of distribution and don't really get it.
« Last Edit: December 23, 2009, 04:56:29 PM by NeilPatrickHarris »

hypnos

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Re: determining the amount of extraction solvent to use?
« Reply #1 on: June 26, 2011, 06:31:12 AM »
This is a good question--I was once pm'd a PDF the said member told me would answer ALL my questions,,unfortunately, I couldnt open the document and the member went AWOL

  Solvents in themselves, are quite a study,,could anyone help here?

Maybe suggest a 'similar' not too involved, yet informative Concise source of information on this topic?

  Trial and error are just too expensive and time consuming...

    thanx Hyppy
"the two things you can give away and never lose, are what you know, and how you feel...."

Winston

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Re: determining the amount of extraction solvent to use?
« Reply #2 on: June 27, 2011, 01:05:51 AM »
If I may suggest, go to your local UNI, and read/borrow, an analytical chem text, which will go into detail regarding solvent extraction, partitioning, etc. There are a number of factors involved, and giving a standard text, a once over, on these issues - could be helpful.

Winston

hypnos

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Re: determining the amount of extraction solvent to use?
« Reply #3 on: June 27, 2011, 04:31:28 AM »
Thanx Winston, and welcome, however, as I mentioned, Solvents are almost a "science in themselves" plus as this IS a site where most of us try to utilise OTC products, I dont want to wade through hundreds of pages of "scientifically written papers" on "the various methods for utilising solvents, which may be nigh impossible for me to obtain.
  I have an acceptable handle on solvents and multiple/combined solvent extractions, but as we tend not to utilise NON OTC (depending on the country) solvents, usually only a small % of those are"Out There for the pro's" to access, its mainly OTC or home synth- this is my prime area of interest
 But thanx for the input, maybe you would like to "Introduce yourself", and any special interests/skills you have you have in the Introductions section.
 Cheers hyppy
« Last Edit: June 27, 2011, 05:15:41 AM by hypnos »
"the two things you can give away and never lose, are what you know, and how you feel...."

lugh

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Re: determining the amount of extraction solvent to use?
« Reply #4 on: June 27, 2011, 06:09:48 AM »
Liquid-liquid extraction depends on the distribution coefficient, therefore it's best to use as small portions of solvent as is practical  ;)  How much one uses depends on how thorough of an extraction is desired  :-X  In some respects it is still an art  8)
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Winston

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Re: determining the amount of extraction solvent to use?
« Reply #5 on: June 27, 2011, 08:00:59 AM »
I am in agreement with lugh, smaller amounts, but greater number of portions is usually better than larger amounts and less number of portions. There is a coefficient rating, compared with, for an eg n-octane, as an eg, with respect to water, where each analyte has a rating, and it can be determined how much of the goods is going to be left behind in the intial batch with successive number of extractions. Something like that, but I am rusty, and I still feel a read up on this stuff is of value, and not as complicated as it may imply.

ps. and thanks for the welcoming
« Last Edit: June 27, 2011, 08:27:39 AM by Winston »
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