1. Liquid Liquid Extraction

7/27/2019 1. Liquid Liquid Extraction

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Liquid Liquid Extraction


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Technique

Liquid - liquid extraction, also called solvent

extraction, is a process that allows theseparation of two or more components due

to their unequal solubilities in two

immiscible liquid phases.


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The Sepration of target Solutes is performed

by shaking the two liquids in a separatory

funnel for a few minutes. The solute which

will be extracted should be soluble with the

both solvents (aquous solution and Organic

Solvent) The solvents should be immiscible with each

other.

The temperature should be same during the

overall extraction process.

The process is done 3 to 4 times for

separation of total solutes from aquous

solution.


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In the liquid liquid extraction process, the

high density containing components is

located at the lower phase and the lowdensity containing components at the upper

phase

In case of Pharmaceutical chemical, two

immiscible organic solvents are used. In

case of Inorganic solutes, aquous solution

is used because inorganic solutes are not

soluble in organic solvent. In case of water sensitive inorganic solutes,

chelate is formed by adding another

component which is also soluble in solvent.


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Principles

An organic solvent is added to the aquous

solution containing solutes and two

immiscible layers are formed.

With moderately shaking the layers aremixed. After mixing, the process is stopped

for few minutes to form two immiscible

layers.

Then the organic layer is boiled to form

precipitation of solutes which is measured.


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PrinciplesThe mixture of solution containing target

solutes and organic solvent is called FEED

PHASE.After extration, the feed and solvent phases

are called Raffinate and Extract


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The distribution of solute follows

the Nernst Distribution Law

Nernst Distribution Law,

Kp= Co/Caq

Kp= the distribution constant

Co= the concentration of analyte in theorganic phase

Caq= the concentration of analyte in theaquous phase


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Crucial and Important Factors in


Error due to Volume change

Effectiveness of an extraction

Factors Influence Solvent Extraction

Effect of Temperature

Effect of pH on extraction


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Factors responsible for slow

coalescence of emulsion

Presence of Finely divided powders

of albumin, gelatin and natural gums. Presence of surfactants in target

solutes

Presence of ionic species at theinterface of two immiscible layers.


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Guidelines to avoid Emulsion

Formation

Very cautious and gentle agitation

Removal of finely divided insoluble

materials

Use of solvent pair having large

density differences and high interfacial

tension

Avoid extreme and particulary high

range of pH

Use of anion exchanger substances


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Techniques used to break an

Emulsion

Mechanical Means

Centrifugation

Addition of monovalent and divalent ions

Addition of Ethanol or higher alcohol

Addition of silicone- defoaming agent

Sudden cooling of emulsion

Altering the ratio of solvents

Passing Emulsion through the Thin bed of

an adsorbent.


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Presentation Group Members

Md. Al-Amin 2006-2-70-076

Md. Golam Tawabul Alam

2006-1-70-028

Md. Tanvir Kabir 2007-1-70-034

Md. Moniruzzaman 2007-1-70-027

Azim Ahmed 2006-2-70-064

Documents

1. Liquid Liquid Extraction