[Golden_4_Life]

When doing a Liquid Liquid Extraction (LLE) such that an aqueous sample that contains organic molecules is targeted for extraction of the said organic molecules using an organic solvent (e.g. methylene chloride, hexane, etc...).
What is the standard ratio of sample volume to organic solvent extractant volume to use when performing an LLE?
Is it typically 1 volume of sample per 2 volumes of extractant or a greater ratio?
Just curious as I'm planning logistics of this new extraction using separatory funnels of maximum volume 30 mL.
So, the basic (no pun intended) question is how much sample volume per volume of organic solv?

[cpncoop]

Hi,

As a rule of thumb, 20 volumes relative to the material weight is about the upper-end of where you want to be for chemical processes, just do to limitations in reactor-size, etc... So for a 1 g sample, I'd put it into 10 mL water and extract 2X w/ 5 mL organic solvent.  You can go to lesser volumes if your material allows it.

[Golden_4_Life]

Thanky Mr. Cooper:
So, according to your "rule of thumb" there ought to be used 10 volumes of organic extractant per 1 volume of sample?
I do not believe that this over-dilute the target analytes as their conc'ns in solution range from 1% to 5% w/w of the solution weight.
Then, you said to extract twice--using a fresh 10 mL aliquot of the organic solvent extractant. 
Is my understanding consistent with what you've proposed?

[cpncoop]

Sorry... Let me clarify. 

If I had a 1 g sample, I would dissolve it in 10 mL water.  I would then extract with 5 mL organic (DCM), split off the organic layer, and extract with a 2nd 5 mL portion of DCM.  I would combine the extracts, giving me a total of 10 mL organic.  Since I started with 10 mL water, that is 20 volumes total....  Hope this helps,

[Golden_4_Life]

YEs, that clarifies. My sample is a liquid state in its native form. So, I will just take 10 mL of it and extract 2x with 50 ml of DCM.

[Golden_4_Life]

I attempted this extraction and got poor UV-vis spectroscopy. I was expectin a sharp peak around 280 - 285 nm but got a crumpled looking peak that began at 215 nm then continued at its same height (AU level) in a jagged fashion through 400 nm.  Perhaps LLE does not give a clean extract or additional cleanup is required afterwards?

[xoto]

just keep trying ratios and test for the presence or absence of target material in source.