Introduction: Liquid-liquid Extraction
Liquid-liquid extraction is a simple extraction technique that exploits relative solubility in order to separate solutes of a solution. This instructable will outline the steps for a simple liquid-liquid extraction and demonstrate proper technique.
The process should take around 4-5 minutes, but varies depending on volume extracted and any repeated extractions.
It should be noted that the instructions. will be based on materials used in this particular instructable and that supplemental instructions should be followed depending on materials used. As such the solvents used include water for the aqueous solvent and acetone for the organic solvent, both of which have been colored for clarity.
Proper laboratory attire should be worn when working with chemicals (gloves, goggles, lab coat etc.)
Follow any safety protocol related to chemicals used in your experiment.
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Step 1: Materials
- Aqueous solution
- Organic solution
- Vial & Cap
- 2 Test Tubes
- Alternatively a separatory funnel (not pictured) can be used instead of a vial and pipette
Step 2: Mix the Solvents
- To the vial, add both the organic solvent and the aqueous solvent. Two separate layers should be observable due to differences in solvent densities. The less dense organic layer will be above the aqueous layer.
- Cap the vial and mix the solution by inverting the vial gently, do not shake too vigorously or you will cause a very fine dispersion of immiscible solvent (emulsion) which will take long to separate.
- NOTE: You should periodically stop and remove the cap while during the shaking process to alleviate any pressure build up that may occur.
- Allow the phases to separate out such that two distinct layers are observed and no noticeable amount of solvents are mixed
Step 3: Separate the Layers
- Extract the layers from one another, make sure to note which layer is organic and which is aqueous (Figure 3.)
- Transfer the layers to separate test tubes to isolate the different solvents.
- Add water to the organic solvent to further extract any aqueous soluble solvents, repeat the steps up until this point and extract the new aqueous layer to the same container.
- At this point you have successfully completed a round of extraction, the process can be repeated to further extract different solutes as per instruction of your particular experiment.
Step 4: Drying the Organic Solvent
A drying agent such as magnesium sulfate can be used to further extract aqueous solvent from the organic solvent after extraction.
- Add drying agent until the organic solvent is sufficiently dried of aqueous solvent. If the drying agent forms a clump at the bottom of the tube, then more drying agent is needed
- Stop once the drying agent begins to swirl around in solution with a 'snowglobe-like' consistency
- At this point the drying agent can be filtered out via vacuum filtration or simple gravity filtration