Liquid-liquid extraction (LLE) : introduction to this sample preparation technique

Liquid-liquid Extraction (LLE) principles

The liquid-liquid extraction (LLE) is one of the oldest sample preparation techniques. It allows , by a physical method , purification or the extraction of classes of compounds (solutes) of the matrix (eluent) wherein they are solubilized.

The extraction solvent should not be miscible with the eluent while solubilizing the maximum of solute. This mixture provides the extract (solvent extraction rich in solutes)
and the raffinate (Eluent depleted in solutes).
Multiply steps extraction allows to deplete the eluent in solute in favor of enriching the extract. This extract is then evaporated to increase the concentration in compounds of interest in the extraction solvent.

The disadvantages of liquid-liquid extraction with a separatory funnel

This technique is a very used step of sample preparation, but it presents multiple drawbacks when practiced with a separatory funnel :

• Multiplication of extraction steps to obtain optimum output
• Use of large volumes of organic solvents, which the costs of recycling are becoming increasingly more expensive
• Emulsion’s difficulties which hinders the full recovery of the extract
• The traces of eluent in the raffinate which requires additional processing of the sample before the evaporation step

New solutions for liquid-liquid extraction more effective, faster and less expensive

To overcome these problems, industrialists have developed new solutions allowing for liquid-liquid extraction on a solid support (or SLE) constituted of diatomaceous earth .
After sample deposition , the eluent (composed preferably of 100 % water) is then absorbed on the solid support , such as ink on a blotting paper. After a few minutes,
the extraction solvent is added to the column. By gravity, the extraction of the eluent is achieved without generating emulsion. The recovered extract is devoided of traces of eluent.
The extraction is faster , more efficient and the volumes of extract evaporated are lower.

The gain of time is such that it compensates the purchase of consumables.

Clean-Elut columns, the Interchim® solution for your liquid-liquid extractions

Developed to multiply and accelerate the liquid-liquid extractions in labs, Interchim® Clean-Elut columns are filled with land of high purity diatomaceous and chemically stable to solvents.
These columns are filled in standard tubes in polypropylene medical grade thus minimizing the quantity of extractable impurities during the passage of organic solvents.
They work simply by gravity, without using the vacuum for flow reproducible and repeatable from column to column.
There is no eluant traces in the recovered extract. Their high exchange capacity allows a very significant extraction efficiency without emulsion.

How to choose your Clean-Elut columns Interchim®

The sample volume used should be at most equal to the volume indicated on the extraction column.
The extraction of acidic compounds can be carried out with columns dabbed to pH 4.5 while columns dabbed at pH 9 are rather reserved for the extraction of basic compounds.