Soxhlet extractor technique

For extraction of solid materials with a solvent, a Soxhlet extractor is commonly used. This technique is applied, for example, in the alcohol extraction of dyes to free them from insoluble contaminants such as sodium chloride or sodium sulfate. 

The samples were col 1 ected on fil ters and extracted for 16 hours in a Soxhlet extractor. Using column chromatography the extract was divided over 2k fractions. The absorbtion spectra of the fractions were measured in the 270-400 nm region. Later in the study, when the PAH concentrations became lower and better laboratory techniques became available, determinations were made by HPLC. 

The commercial aluminum-polyethylene composite film was kept in a soxhlet extractor and xylene was used in a 14-hour extraction to remove the polyethylene from the composite film. After removal of the polyethylene film the remaining film was rinsed by ethyl alcohol and dried. The dried film was used in the study of aluminum-polyethylene "free interface by AES depth profile technique. 

The technique of liquid-liquid extraction was described in Sections 12.1-12.8. In this section, solid-liquid extraction is described. Solid-liquid extraction is often used to extract a solid natural product from a natural source, such as a plant. A solvent is chosen that selectively dissolves the desired compound but that leaves behind the undesired insoluble solid. A continuous solid-liquid extraction apparatus, called a Soxhlet extractor, is commonly used in a research laboratory. 

Base- and acid-catalyzed aldol reactions of aldehydes generally lead to useful amounts of aldol product, the p-keto alcohol, or the product of dehydration, the a,P-unsaturated carbonyl compound. Aldol reactions of ketones are less useful because equilibrium does not usually favor product. Special techniques can be used (Soxhlet extractor) to thwart thermodynamics. If dehydration to the a,P-unsaturated carbonyl compound occurs, as it often does in acid-catalyzed aldols, the reaction may be practically successful. 

Soxhlet extraction is the most commonly used technique to quantitatively remove PCDDs and PCDFs from solid environmental matrices (such as sediments, fly ash, particulate matter) and solid sorbents employed in air or water sampling. A Dean-Stark apparatus is often used in combination with the Soxhlet extractor to remove traces of water [13]. Besides the classical Soxhlet apparatus, other innovative techniques have been developed for the extraction of organic substances from solid matrices. Among these techniques, the pressurized fluid extraction (PEE) found wide acceptance in the scientific community. 

If a solid substance is extracted repeatedly with several portions of cold solvent, the operation is called maceration, if the same operation is carried out with hot solvent, it is called digestion and if the procedure has a countercurrent character, it is called percolation. So-called Soxhlet extractors, in which a solid substance is extracted with a solvent and the extract becomes more and more concentrated, function automatically. If a dissolved substance is extracted with one portion or more of an immiscible solvent, the operations is called simple extraction or multiple extraction, respectively. If the extraction is carried out by countercurrently-moving solvents, we deal with a countercurrent distribution technique. A continuous extraction of a liquid with another liquid immiscible with the first is called perforation continuous countercurrent extraction using two liquid phases is carried out in special countercurrent columns. If one of the phases is fixed on a carrier, partition chromatography is the name given to the operation. The choice of the given type of extraction method will depend on the character of the analyzed substances and on the required separation efficiency. 

Initial Extraction Technique Continuous extraction apparatus was employed, including an extractor designed to contain the starting plant materials, a distillation flask to hold the solvent mixture, the flask being equipped with a reflux condenser, a drip device to facilitate the removal of the volatilized mixture from the condenser and to percolate it through the continuous extractor, and a Soxhlet type return. Means for heating the continuous extraction system were provided. 

The appropriately prepared sample can then be extracted by a number of techniques. The main points to consider are to allow adequate time of exposure of the solvent system in the sample matrix and to limit sample handling steps, that is, avoid filtration steps by using soxhlet (sample in a glass thimble), extraction columns (sample matrix eluted after soaking in soxhlet), or semiauto mated systems (pressurized liquid extractors). 

Neither soxhlet extraction nor steam distillation is designed to isolate volatiles from solids for subsequent determination. Slurrying the solids in water and then applying the PaT procedure has been reported A vacuum extractor with cryogenic concentration has been applied to both fish and sediment samples for determination of volatile priority pollutants PaT, LLE, and static headspace techniques have all been applied to the determination of volatiles in sludges from municipal waste treatment plants... 

The solvent technique for concentrating surfactants is not discussed here. See Ref. [40] for details. Morales-Munoz et al. discuss a screening method for LAS in sediments. It is based on water Soxhlet extraction assisted by focused microwaves. The extractor is coupled with an online preconcentrator/derivatization/detection manifold through a flow injection interface [107]. 

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