What is Soxhlet extractor?
Soxhlet extractor definition
, also known as fat extractor, is composed of three parts: extraction bottle, extraction tube, and condenser, with siphon tube and connecting tube on both sides of the extraction tube respectively, and the connection of each part is tight without air leakage. When operating, the heating temperature can be adjusted according to the different boiling points of reagents and ambient temperature, and the sample is repeatedly soaked and extracted in the extraction process, to achieve the purpose of rapid extraction laboratory extraction apparatus.
Application of Soxhlet extractor
are widely used for the determination of crude fat content. Fat is widely present in the seeds and fruits of many plants, and the determination of fat content can be used as an indicator to identify its quality.
Soxhlet extractor working principle
Soxhlet extraction apparatus works on the principle of solvent reflux and siphoning, so that the solid material can be extracted for pure solvent every time, so the extraction efficiency is high. The solid material should be finely ground before extraction to increase the area of liquid leaching. Then the solid material is placed in a filter paper sleeve and placed in the extraction chamber. Install the apparatus. When the solvent is heated to boiling, the vapor rises through the pilot tube and is condensed into a liquid drop into the extractor. When the liquid level exceeds the highest point of the siphon tube, the siphoning phenomenon occurs and the solution flows back into the flask, so that some of the material dissolved in the solvent can be extracted. In this way, the solvent reflux and siphoning are used to enrich the soluble material in the solid into the flask. Before each siphon, the solids are extracted by the pure hot solvent, and the solvent is repeatedly used to shorten the extraction time, so the extraction efficiency is higher.
For extraction, the sample to be measured is wrapped in a skimmed filter paper packet and placed in the extraction tube. When the extraction bottle is heated, the petroleum ether will be vaporized, and will rise from the connecting tube into the condenser and condense into a liquid drop into the extraction tube to extract the lipids from the sample. When the liquid level of petroleum ether in the extraction tube reaches a certain height, the petroleum ether dissolved in crude fat flows into the extraction bottle through the siphon tube. The petroleum ether flowing into the extraction bottle continues to be heated and vaporized, rises, condenses and drips into the extraction tube, and so on, until the extraction is complete.
As the organic solvent extracts in addition to fat, but also contains more or less free fatty acids, sterols, phospholipids, waxes and pigments and other lipid-like substances, and thus the results of the Soxhlet extraction method can only be determined crude fat.
Advantages of using Soxhlet extractor
The main advantages of using the Soxhlet extraction equipment are as follows.
Good selectivity of Soxhlet extractor
The selectivity of Soxhlet extraction depends mainly on the similarity of the properties of the target substance and the solvent. The extractants can be used as CS2, benzene, methanol, etc. The common practice is to extract the extractants in multiple stages in the order of different polarity. Thus, the extraction purity of the product is improved. The different classes of substances are extracted separately.
Low energy consumption of Soxhlet extractor
Since the extractant is heated directly by the cable extraction, and the extractant is generally chosen to have a low boiling point, the rapid conduction and full utilization of energy are fundamentally ensured. Moreover, the extractant is recycled in the soxhlet extractor, which not only reduces the amount of solvent but also shortens the operation time and greatly reduces energy consumption. And the degree of completion of extraction is high. It is possible to extract solvent several times and the utilization rate is relatively high.
Simple equipment and easy operation
Different separation methods have different operation methods, and the corresponding experimental equipment is also different. However, the equipment of Soxhlet extraction is simple and easy to operate. And its low cost and small size make it suitable for laboratory applications.
Selection of extraction solvent for Soxhlet extractor
When choosing the extraction reagent for the Soxhlet extraction device
, the law of similarity and solubility can be used for selection. Fat polarity in agricultural products is generally small, petroleum ether or ether can be used as extraction reagents. There are two kinds of petroleum ether for common laboratory use: low boiling range (30~60℃) and high and low boiling range (60~90℃), and it is generally good to choose low boiling range petroleum ether as extraction solvent to shorten extraction time. If you choose ether as the extraction reagent, you must pay close attention to the safe use of ether. The presence of open flame or heating with open flame should be strictly prohibited in the extraction room. The ether should not contain peroxide and the extraction room should be well ventilated to prevent combustion and explosion. The method of checking the peroxide in ether is: take an appropriate amount of ether, add potassium iodide solution, shake vigorously and place it for 1min, if it appears yellow, it indicates the presence of peroxide and should be treated before use. The treatment method is: put the ether into the partition funnel, first with 1/5 ether amount of dilute KOH
solution washed 2~3 times to remove ethanol; then acidified with hydrochloric acid, add 1/5 ether amount of FeSO4 or Na2SO3 solution, shake, let stand, discard the lower layer of aqueous solution after stratification to remove peroxide; finally washed with water to neutral, dehydrated with anhydrous CaCl2 or anhydrous Na2SO4 and redistilled.
Soxhlet extractor specifications and features
Glass Soxhlet extractor
Glass Soxhlet extractor uses high borosilicate glass, heat resistant and high temperature resistant.
Automatic Soxhlet extractor
|Number of extracted samples per batch
|Extraction bottle volume
|Extracted sample volume
|Temperature control range
|room temperature +5℃~100℃
|Power supply voltage
|220V +10V frequency 50Hz
|Electric heating power
1. Automatic Soxhlet extractor consists of three major parts: heating and extraction, solvent recovery and cooling, fully automatic process operation, automatic solvent recovery, and time saving.
2. The heating temperature can be adjusted according to the boiling point of the reagent and the ambient temperature.
How to use Soxhlet extractor?
Here is how to operate the Soxhlet extractor.
1. Fold the filter paper cartridge and place the folded cartridge into the cartridge holder, requiring the cartridge opening to be neither higher nor lower than the metal opening of the cartridge holder. Put a layer of skimmed cotton into the bottom of the filter paper cartridge and press it firmly. The thickness of the press is about 2mm.
2. Weighing: For low-fat samples such as grain and feed, the crushed sample can be weighed directly at about 2 grams, 0.0002 grams. Transfer the sample into the filter paper cartridge, cover with another layer of skimmed cotton, pressed tightly to the mouth of the filter paper cartridge. Then put it into the aluminum cup, which is kept clean inside and outside.
3. Transfer the filter paper cartridge holder and the aluminum cup together into the bracket, pull up the handle, suck the filter paper cartridge holder onto the upper speed section, and pull down the handle. Loading all the samples individually.
4. Put the tray into the instrument, depress the lever and lock it. Check that the aluminum cups are not offset. Pull up the handle and dip the cartridge holder into the aluminum cups. Start soaking.
5. Set the temperature. After soaking time, pull down the handle and start the extraction process. Refer to the table in the instruction manual for the extraction time.
6. Turn the knob to horizontal position for solvent recovery after extraction time. The solvent is recovered in the glass bottle above the knob and the power is turned off after the solvent is recovered.
Soxhlet extractor precautions
The following are precautions to take when using the Soxhlet extractor
1. In the Soxhlet extraction, the sample is generally loaded with filter paper cartridges, should not use metal sieve cartridges because it will cause the decomposition of some pesticide targets, for example, Fe may lead to the decomposition of some organic chlorine pesticides. In addition, care should be taken to match the filter paper cartridge with the extractor after loading the sample, especially attention must be paid to the paper cartridge can not block the siphon return tube.
2. The Soxhlet extractor used in the experiment should not be too large, otherwise the solvent vapor reaches the extractor before the condensation of the ambient air and reduces the extraction efficiency, which makes the extraction time too long.
3. Since Soxhlet extraction is a relatively open extraction system, care should also be taken to prevent contamination during the extraction operation; the top of the condenser tube will be covered during the experimental operation.
4. Soxhlet extraction tube cleaning, you can generally use chromic acid washing solution for cleaning, deionized water (can be used before the preparation of more with hexane extraction for a backup) in the clean, dry or air dry.
How to order Soxhlet extractor?
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