Extraction from solid material

This method, developed at the end of the 19th century, is still the most widely used when organic compounds have to be extracted from solid materials, like dusts, sand, soil, and marine sediments. It is particularly suitable when the organic material is strongly adsorbed on a porous solid matrix. Such a simple method presents several advantages the sample is repeatedly brought into contact with fresh portions of the solvent and no filtration is required after the leaching step, simultaneous extraction in parallel can be performed since the basic equipment is inexpensive, and finally it has the possibility to extract more sample mass than most of the latest methods [microwave extraction,... 

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. 

Milbemectin consists of two active ingredients, M.A3 and M.A4. Milbemectin is extracted from plant materials and soils with methanol-water (7 3, v/v). After centrifugation, the extracts obtained are diluted to volume with the extraction solvent in a volumetric flask. Aliquots of the extracts are transferred on to a previously conditioned Cl8 solid-phase extraction (SPE) column. Milbemectin is eluted with methanol after washing the column with aqueous methanol. The eluate is evaporated to dryness and the residual milbemectin is converted to fluorescent anhydride derivatives after treatment with trifluoroacetic anhydride in 0.5 M triethylamine in benzene solution. The anhydride derivatives of M.A3 and M.A4 possess fluorescent sensitivity. The derivatized samples are dissolved in methanol and injected into a high-performance liquid chromatography (HPLC) system equipped with a fluorescence detector for quantitative determination. 

Much of the interest in SFE has been focused on using carbon dioxide to extract different natural products from solid materials. Examples of large industrial processes in this area are decalfeinating coffee beans and hop extraction. 

The leaching conditions of a ultrasound-assisted device were studied to obtain the best experimental settings Microwave acid extraction was implemented to recover metals from solid materials. The operational conditions needed to form the hydrides were set after ana-... 

In this Chapter, fundamentals of design criteria in relation to processes and equipment are reviewed for dense-gas-extraction from solid matrices. Although, as mentioned in previous chapters, numerous dense gases can be used as solvents. In the following discussion we concentrate on the most extensively used gas-carbon dioxide. The reason for this is its nontoxic, non-flammable and inert nature, the possibility of gentle treatment of thermally sensitive materials, and the fact that it is inexpensive and an environmentally acceptable material. 

Supercritical Fluid Extraction and Fractionation from Solid Materials E. Lack0, B. Simandi ... 

Coal and Coal-Tar Hydrogenation. If paraffinic and olefinic liquids are extracted from solid fuel substances, the hydrogen content of the residual material is reduced even further, and the residues become more refractory. The yields of liquids so derivable are generally low, even when a significant fraction of the hydrogen is extractable. Thus production of fuel liquids from nonliquid fuel substances such as coal and coal tars may be enhanced only by the introduction of additional hydrogen in a synthesis process. The principal differences in the processes are from the modes in which hydrogen is introduced and the catalysts used. 

To prepare water and water-ethanol (1 1) extracts of fresh juices, 2g of the sample is added to 10 ml of extragent and stored at room temperature for 18-24 h. The extract is separated from solid material with glassy filter (pore size 100-160 pm) and analyzed as follows ... 

Concrete The aromatic, waxy or fatty extract from plant material obtained by washing with a hydrocarbon solvent (such as hexane). Concretes are usually solid or semi-solid and contain essential oil, wax and soluble plant materials like pigments. 

Extraction of Forms of Elements from Solid Materials and Concentration of Solutions... 

For extraction from solid samples, e.g., biological materials and homogenates (planf tissue, food), liquid extraction can be applied using for instance acetone, methanol, or acetonitrile. Often, extracts are filtered prior to injection to LC-MS. 

Separation by Centrifugal Force.—The three possible separations which can be made by centrifugal machines are (1) The extraction of liquids from solid material, such as textiles, fibers, leather, crystals, etc. Examples of this mode... 

The extraction of bile acids from solid material, such as feces or tissues, requires a different approach since bile acids are likely to be firmly bound to bacteria or proteins. A variety of solvents have been used, such as alcoholic alkali (G14), toluene-acetic acid (E4), methanol-acetone (B35), and methanol-chloroform (El), sometimes with refluxing or Soxhlet extraction (B17, El). The state of ionization of the carboxyl group of bile salts, and thus the solvent pH, would be expected to affect the efficiency of extraction with organic solvents, with better extraction at acid pH. However, in practice an... 

Fractionation of liquid mixtures with supercritical carbon dioxide in counter-cur-rent columns can be operated continuously, because liquids can be easily pumped into and out of a column. This represents a big advantage over extrachon from solid materials, as it allows real process intensification - large quantities of feed can be processed with only a small volume under high pressure at any given time. Frac-tionahon, mostly of natural products or extracts, has been extensively studied at the laboratory and pilot-plant scale. The design principles of this type of column have been established, and scale-up procedures devised [1,6]. They can be operated with reflux, as in distillation, and frachonahon can therefore become an extremely se-lechve process. Difficult separahons can be effechvely carried out. 

The classical method for isolation of humic substances from solid-phase source materials such as soils, peat, and leonardite is alkaline extraction with aqueous NaOH, followed by precipitation of humic acid at low pH, and a series of desalting steps involving cation exchange, dialysis, etc., to obtain fulvic acid. Through this procedure, samples extracted from solid-phase materials include both... 

Bniiuier, G. (1984) Mass transfer from solid material in gas extraction, Benchte Bunsenges. Phys. Chem. 88,887- 891. 

The extraction of components from solid material is carried out by contacting the solid substrate with a continuous flow of the supercritical solvent. The solid substrate in most cases forms a fixed bed, through which the supercritical gas flows and extracts the product components until the substrate is depleted. For the solid as well as for the solvent, this is an unsteady process. The course of the extraction process can be followed by determining the amount of extract against time of extraction. From these data, more information on the process can be deducted, which is discussed below. 

Model for Extraction from Solids Using Supercritical Solvents Extraction from solids with supercritical gases can be a complicated process if the two phase flow, the properties of the solid material, and the inhomogeneities of the fluid and the solid phases have to be considered. For most cases, a far simpler model is sufficient. In the proposed model, the following parameters are considered sufficient to calculate the progress and the result of an extraction [3,4] ... 

Multistage countercurrent contacting is the most effective mode. It reduces the amount of solvent and makes possible continuous production of extract. Real countercurrent contact is not easily established for solids, since special effort is necessary for moving the solid, with increased difficulties at elevated pressure. Therefore, it is easier to not move the solid material and to achieve countercurrent contact by other measures. For the purposes of extraction from solids with supercritical solvents, several fixed beds in countercurrent contact with the solvent are the best configuration (Fig. 11). 

Increased efficiency in extraction leads directly to a reduction in material wastage and power ultrasound has been shown to improve systems as diverse as coal slurry benefication on a tonne scale to medicinal compound extraction from plant materials. The classical techniques for extraction are mainly liquid-solid extraction by means of steam and/or organic solvents. All such techniques use relatively high temperatures and thus the energy consumption is very high and decomposition of some compounds may also occur. The use of ultrasound avoids these high temperatures and can result in enhanced component extraction at lower temperatures and in a faster time. 

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