What is Liquid-liquid extraction?
is also known as solvent extraction
. It is a scientific device for the process of separating and extracting components of a liquid mixture with a solvent. A selected solvent that is not miscible or slightly miscible is added to the liquid mixture, and the different solubility of its components in the solvent is used to achieve separation or extraction purposes.
Application of Liquid-liquid extraction
Liquid-liquid extraction equipment
is a very common pre-treatment operation in laboratories at all levels, such as the separation of phenol from coal tar using benzene as a solvent, and the recovery of acetic acid from dilute acetic acid solution using isopropyl ether as solvent. It is performed in laboratories with instruments such as partition funnels. In industry, it is carried out in packed towers, sieve plate towers, centrifugal extractors, spray extractors, etc. Liquid-liquid extractor is widely used in organic chemistry, petroleum, food, pharmaceutical, rare elements, atomic energy, water quality pretreatment, anionic surfactant pretreatment in water and other laboratory fields.
Liquid-liquid extraction working principle
The working principle of liquid-liquid extractor is to use the difference in solubility or partition coefficient of a compound in two mutually insoluble (or slightly soluble) solvents to transfer the compound from within one solvent to the other. After iteration of extraction, the majority of the compounds were extracted.
The law of partitioning is the main basis of the theory of extraction methods, where substances have different solubilities for different solvents. At the same time, when a soluble substance is added to two insoluble solvents, it can be dissolved in the two solvents respectively. It is proved that the ratio of this compound in the two liquid layers is a constant value at a certain temperature when the compound does not undergo decomposition, electrolysis, conjugation, and olventization with these two solvents. This is true regardless of the amount of the substance added. It is a physical change. It is expressed by the formula.
K is a constant called "partition coefficient".
The solubility of organic compounds is generally higher in organic solutions than in water. Extraction of compounds dissolved in water with organic solvents is a typical example of extraction. In extraction, if a certain amount of electrolyte such as sodium chloride is added to the aqueous solution, the "salting effect" is used to reduce the solubility of the organic compound and the extraction solvent in the aqueous solution, which can often improve the extraction effect.
To completely extract the desired compound from the solution, usually, one extraction is not enough and must be repeated several times.
Advantages of using liquid-liquid extraction
The advantage of using liquid-liquid extraction is that it can be the principle of using air pressure to fully combine the water sample and extractant and fierce collision to achieve the purpose of complete extraction. Completely replace the manual shaking, reduce the labor intensity of laboratory personnel, avoid direct contact between human and toxic reagents, and protect the health of the operator, and the whole extraction process without manual bleeding, automatic liquid discharge, or automatic cleaning. At the same time, it also greatly reduces the pollution of the environment, improves extraction efficiency, and makes the analysis results stable and reliable.
Liquid-liquid extraction solvents
Liquid-liquid extraction solvents
are chemical reagents that can form an extractive compound with the extracted material dissolved in the organic phase. Common extraction solvents include benzene, carbon tetrachloride, alcohol, kerosene, straight-run gasoline, etc.Benzene
Benzene is a hydrocarbon, the simplest aromatic hydrocarbon, which is a sweet, flammable, carcinogenic, and toxic colorless transparent liquid at room temperature with a strong aromatic odor. It is insoluble in water, easily soluble in organic solvents, itself can also be used as an organic solvent.Carbon tetrachloride
Carbon tetrachloride is a colorless and toxic liquid that can dissolve fat, paint, and many other road substances, volatile liquid with a slightly sweet odor of chloroform. Carbon tetrachloride and water are mutually insoluble and can be miscible with ethanol, ether, chloroform, and petroleum ether.
Alcohol is an organic substance, within the most common mono-alcohol. Ethanol at room temperature and pressure is a flammable, volatile colorless transparent liquid, low toxicity, pure liquid not directly drinkable; has a special fragrance, and slightly irritating; slightly sweet, and accompanied by a stimulating pungent taste.Kerosene
Kerosene mainly refers to a chemical substance, which is a class of light petroleum products. It is obtained by fractional distillation or cracking from natural petroleum or artificial petroleum. The term "kerosene" alone generally refers to lighting kerosene.
Liquid-liquid extraction specifications and features
Automatic liquid-liquid extraction
|Number of extracted samples per batch||4
|Extraction bottle volume|| 250ml/each
|Extracted sample volume|| 0-5g/each
|Maximum heating temperature|| 100℃
|Temperature control accuracy||±0.5℃
|Power supply voltage|| 220V.50Hz
|Electric heating power||1000W
1. The material of automatic liquid-liquid extraction is made of sanitary stainless steel with plastic spray.
2. High extraction efficiency ≥95%. Fast extraction speed, 3 minutes to extract multiple samples at the same time.
3. High degree of extraction automation, while extracting and degassing.
4. Avoid direct contact between the experimenter and the toxic extraction solvent, suitable for all liquid-liquid extraction work.
Triplex liquid-liquid extraction
|Working voltage|| 220V AC
|Temperature control range|| room temperature +5℃-90℃
|Electric heating power||Electric heating power 600W
1. Triplex liquid-liquid extraction has high extraction efficiency ≥ 98%, fast extraction speed, 1 minute to extract a sample.
2. High reproducibility, recovery of 97-100%
3. Simple operation, low noise, save time and effort, easy to clean, can be disassembled integration.
How to use liquid-liquid extraction?
Here is how to use the liquid-liquid extraction equipment
1. Take out the extraction bottle and place it on the hole of the instrument support plate;,then insert the liquid-liquid column into the corresponding extraction bottle.
2. Take out the air guide tube, connect one end with the exhaust hole on the base of the instrument, and the other end with the well air port of the liquid-liquid column, note that, if there is no ventilation device, the exhaust port on the liquid-liquid column can be connected to the outdoor with the air guide tube.
3. Take a certain amount of water samples (such as 500ml water samples) from the extraction bottle mouth slowly pour in, and then take a certain amount of extractant such as 50mL carbon tetrachloride from the extraction bottle mouth slowly pour in.
4. Close the switch after 1 minute of violent reaction between the water sample and the extractant, stand still and wait for the liquid to stratify, unscrew the liquid valve and release the extracted liquid, the extraction is finished.
How to maintain liquid-liquid extraction?
1. Proper use and attention to the maintenance of liquid-liquid extractor, so that it is in good working condition, can extend the service life of the instrument.
2. When the solvent extraction is working normally, the center of gravity is stable and the noise is small. When the instrument noise is found to be abnormal, it should be stopped to check whether the fasteners are loose.
3. Liquid-liquid extraction instrument during continuous work, should be done quarterly check: check whether there are water droplets, dirt attached to the instrument devices, if so, need to clean up in time.
4. Liquid-liquid extraction instrument after long-term use, natural wear and tear is a normal phenomenon. After one or two years of use, if the instrument is found to be abnormal noise, device insensitive phenomenon, should be promptly repaired.
5. In the process of use, if touching the liquid-liquid extractor feel numb electricity, abnormal sound, pungent smell, smoke and other abnormal phenomena, please immediately cut off the power to stop using, and promptly contact the after-sales service.
6. Frequently check the power cord plug and socket should be in good contact, reliable, and well grounded, no overheating phenomenon.
7. Liquid-liquid extractor without waterproof function, prohibit the body of the instrument in water, otherwise it will cause poor insulation, resulting in leakage and failure. In case of special circumstances leading to water inside the instrument, please immediately cut off the power supply and stop using the instrument, and promptly contact the after-sales service.
8. Liquid-liquid extractor instrument should avoid more moisture to reduce the chance of rusting of metal parts.
9. The exterior of liquid-liquid extractor instrument is only partially anti-corrosion, if strong acid, strong alkali, organic solvent and other reagent drops splash to the surface of the instrument, please immediately cut off the power and stop using, and wipe clean in time; if a large amount of reagent is spilled to the interior of the instrument, please immediately cut off the power and stop using, and promptly contact after-sales.
Precautions for using liquid-liquid extraction
The following are the precautions for using liquid-liquid extraction,
1. irst of all, check whether the liquid is leaking before use, check whether the top plug of the fractionation funnel and the piston are leaking, check with water, and make sure there are no leaks before using the extraction equipment.
2. Pour the extracted liquid and the extractant into the funnel from the upper mouth in order, usually 1∕3 of the volume of the extracted liquid, and tighten the top plug.
3. Before releasing the liquid, uncork the bottle, then slowly turn the piston open and release the lower layer of liquid from the piston to the receiving bottle.
4. When releasing the liquid, remember that the lower layer is the denser liquid and should be released from below. The upper layer is a relatively small density of liquid, pour out from above.
5. The liquid-liquid extractor should be cleaned immediately after use.
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