Extraction techniques refluxing

Dissolution of the powder. After homogenising the powder, obtained either directly by drilling or by cmshing core shces, a part is weighed precisely and dissolved in a constant amount of liquid, most frequently in concentrated nitric acid solution with ISA (ionic strength adjuster). In this way the total or acid soluble chloride content is determined. The dissolution process is the most important step determining the reproducibility of the chloride analysis. Alternatively, the Soxhlet extraction technique (reflux of boiling water on the concrete powder for 24 h) is used to dissolve chloride ions. Both methods result in a similar total chloride content. 

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 Soxhiet type return. Means for heating the continuous extraction system were provided. 

Extraction techniques for polymeric matrices can be divided into traditional and new . The traditional techniques include Soxhlet extraction, boiling under reflux, shaking extraction and sonication. All these methods are at atmospheric pressure. When the sample is added to a solvent, which is boiled under reflux (i.e. at the highest possible temperature without applying an external pressure) extractions tend to be much faster than Soxhlet extractions. Examples are the Soxtec ,... 

Table 3.6 Relative efficiencies of microwave-assisted and reflux extraction techniques for additives in LDPE ...

The acid-catalyzed equilibrium of a dibasic acid with its mono- and di-esters furnishes a means of preparation of alkyl hydrogen esters of most aliphatic a,o)-dibasic acids. A mixture of the acid and its dialkyl ester is refluxed with concentrated hydrochloric acid and dibutyl ether, and the add ester is isolated by fractional distillation or extraction techniques. Excellent directions are given for the acid esters of adipic, sebacic, and azelaic acids. 

Soxhlet extraction is used as the benchmark against which any new extraction technique is compared. The basic Soxhlet extraction apparatus consists of a solvent reservoir, an extraction body, a heat source (e.g. an isomantle) and a water-cooled reflux condenser (Figure 7.2). A Soxhlet uses a range of organic solvents to remove organic compounds, primarily from solid matrices. The solid sample (ca. 10 g if a soil) and a similar mass of anhydrous sodium sulfate are placed in the porous thimble (cellulose), which in turn is located in the inner tube of the Soxhlet apparatus. The apparatus is then fitted to a round-bottomed flask... 

The present study compared the ability of three techniques to extract PAH compounds and their alkylated homologues from marine sediments. Specifically, this study was designed to determine if the results of a shorter and simpler extraction (CH2C12 reflux) were comparable with those from longer yet more commonly used extraction methods (exhaustive soxhlet and ball-mill tumbling). 

Unfortunately the water soluble techniques produce results that are difficult to reproduce so they are rarely used in the United Kingdom or Europe, although the soxhlet extraction technique , a method of refluxing concrete chips in boiling water to extract the chloride is a standard technique used in North America. See, for example, AASHTO T260 Sampling and Testing for Total Chloride Ion in Concrete and Concrete Raw Materials which includes a procedure for water soluble ion sample preparation and analysis. 

In the pharmaceutical field, PFE has also been used for two primary purposes, namely to extract pharmacologically active substances from plants and, especially, for quality control of tablets and medical foods. In this field, PFE clearly surpasses classical extraction methods such as those endorsed by pharmacopeias (which use as official standards techniques such as Soxhlet extraction, percolation, maceration, digestion, extraction under reflux, and steam distillation) and others based on ultrasonica-tion or turboextraction. PFE is a firm candidate for use in high-throughput screening programs for natural product discovery, where large numbers of small-scale extractions have to be performed in an efficient, reproducible manner. 

This is a reflux-type extraction technique in which a solid sample is put in a thick, stiff paper thimble, in which solvent repeatedly fills and siphons. The analyte is exhaustively extracted, usually over a period of hours, without operator intervention. Soxhlet extraction was used in the TLC determination of the main alkaloid, tetrandrine, of Stephania tetrandra (methanol-5% cone, ammonia solvent) lipids from grain sorghum DDG (n-hexane solvent) "" and secondary amines from some Nigerian foodstuffs (petroleum ether, 60-90°C, solvent)." ... 

Extraction techniques. Various procedures for the extraction of additives from polypropylene have been reported [1-6], many directly coupled to techniques such as GC, HPLC or UV-visible spectroscopy. Some use Soxhlet extraction or extraction under reflux with solvents such as chloroform, hexane or diethyl ether. Others use a dissolution procedure with solvents such as toluene or xylene followed by precipitation of the polymer, either by the addition of methanol or ethanol or by cooling. A more recent development has been the use of a microwave oven for the rapid extraction in 3-6 min of additives from polypropylene [7]. 

Peterson SC, Eller FJ, Fanta GF, Felker FC, Shogren RL. 2008. Comparison of the effects of critical fluid and reflux-extracted techniques on com starch pasting properties. Carbohydr Polym 71 74-79. 

Dual solvent fractional extraction (Fig. 7b) makes use of the selectivity of two solvents (A and B) with respect to consolute components C and D, as defined in equation 7. The two solvents enter the extractor at opposite ends of the cascade and the two consolute components enter at some point within the cascade. Solvent recovery is usually an important feature of dual solvent fractional extraction and provision may also be made for reflux of part of the product streams containing C or D. Simplified graphical and analytical procedures for calculation of stages for dual solvent extraction are available (5) for the cases where is constant and the two solvents A and B are not significantly miscible. In general, the accurate calculation of stages is time-consuming (28) but a computer technique has been developed (56). 

This technique is used to extract effectively analytes that are polar in nature and strongly bound to soil. Typically, a solvent mixture containing a water-miscible solvent and an apolar solvent (e.g. methanol-dichloromethane) is used. A small aliquot of soil (10-30 g) is dried by mixing with sodium sulfate and refluxed for 8-16h to extract the residues. 

Isolation of the products from complex matrixes (e.g. polymer and water, air, or soil) is often a demanding task. In the process of stability testing (10 days at 40 °C, 1 h at reflux temperature) of selected plastic additives (DEHA, DEHP and Irganox 1076) in EU aqueous simulants, the additive samples after exposure were simply extracted from the aqueous simulants with hexane [63]. A sonication step was necessary to ensure maximum extraction of control samples. Albertsson et al. developed several sample preparation techniques using headspace-GC-MS [64], LLE [65] and SPE [66-68]. A practical guide to LLE is available [3]. 

A common technique used for polyolefin samples is to dissolve the sample using solvents such as xylene, decalin, toluene and di- or trichlorobenzene heated to temperatures as high as 130-150°C. After the plastic sample has been solvated, the polymeric component is precipitated by cooling and/or by adding a cold nonsolvent such as acetone, methanol or isopropanol. Polypropylene does not completely dissolve in toluene under reflux for 0.5 to 1 h with magnetic stirring (typically, 2g of polymer in 40 mL of toluene), yet the additives may be extracted [603]. In addition to additives, most solvents also extract some low-MW polymer with subsequent contamination of the extract. To overcome this a procedure for obtaining polymer-free additive extracts from PE, PP and PS has been described based on low-temperature extraction with n-hexane at 0°C [100],... 

Studies on the use of hydrothermal, microwave-assisted, and reflux synthesis methods for the development and application of nanomaterials have been reviewed. An important aspect of the green synthesis of metallic nanopartides involves techniques that make use of biological materials such as plant extracts and microorganisms. The design of nanomaterials and control of their desired properties have been reviewed. The unique properties of manufactured nanomaterials offer many potential benefits. 

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