Filtration liquid-solid extraction

In liquid-solid extraction (LSE) the analyte is extracted from the solid by a liquid, which is separated by filtration. Numerous extraction processes, representing various types and levels of energy, have been described steam distillation, simultaneous steam distillation-solvent extraction (SDE), passive hot solvent extraction, forced-flow leaching, (automated) Soxh-let extraction, shake-flask method, mechanically agitated reflux extraction, ultrasound-assisted extraction, y -ray-assisted extraction, microwave-assisted extraction (MAE), microwave-enhanced extraction (Soxwave ), microwave-assisted process (MAP ), gas-phase MAE, enhanced fluidity extraction, hot (subcritical) water extraction, supercritical fluid extraction (SFE), supercritical assisted liquid extraction, pressurised hot water extraction, enhanced solvent extraction (ESE ), solu-tion/precipitation, etc. The most successful systems are described in Sections 3.3.3-3.4.6. Other, less frequently... 

Liquid-solid extraction followed by filtration or centrifugation... 

The use of the Zymate Laboratory Automation System allows the standardization and automation of many routine operations in an analytical chemistry laboratory. It additionally allows for a closing of the analytical automation loop of sample preparation and analysis therefore potentially decreasing the need for personnel with a resultant increase in productivity. These operations include, but are not limited to, weighing, pipetting, diluting, blending, heating, liquid-solid extraction, and filtration. 

For the extraction of complex matrices, such as food, procedures based on ion-pair extraction using a tetrabutylammonium (TBA) hydroxide solution are widely employed [64,65]. However, this method has some disadvantages, such as (a) coextraction of lipids and other matrix constituents and (b) the wide variety of recoveries observed, which are related to the matrix effects mentioned previously. Liquid-solid extraction (LSE) is also applied to the analysis of biota and food samples [66]. During recent years, KOH digestion, to release covalently-bound fluoride ions followed by extraction using solid-phase extraction has been used. This method was initially reported by Yamashita et al. [67] and later applied in different studies [68]. For liquid samples, analysis protocols based on filtration followed by SPE are widely used. 

In general, liquid/solid extraction methods offer the simplicity of solution phase synthesis and the ease of work-up by simple filtration normally offered by solid phase synthesis. As such, their use will almost certainly become much more widespread in the future. 

Two-phased samples, where the components of interest are present in high concentration in the liquid, can often be dealt with by simple filtration as the amount of material adsorbed on the surface of the solid phase, relative to that in the liquid phase is likely to be insignificant. Alternatively if the material is dispersed as a solid throughout the solid phase, then the sample can be filtered and the solid extracted exclusively. 

The SRC-I process, developed by the Pittsburg Midway Coal Mining Co. in the early 1960s, was not really a hquefaction process rather, it was designed to produce a solid fuel for utility applications. Only enough liquid was produced to keep the process in solvent balance. The bottoms product was subjected to filtration or solvent extraction to remove ash and then solidified to produce a low-ash, low-sulfur substitute for coal. However, the value of the product was not high enough to make this process economically viable. 

In a 250-mL, round-bottomed flask equipped with magnetic stir bar, 1-bromoadamantane (35.0 g, 0.16 moles) is dissolved in 3,5-dimethylanilinef (92.0 g, 0.75 moles), yielding a clear, pale yellow solution. This is heated under nitrogen for 24-36 h at 140°C to form a thick brown liquid. The reaction is conveniently monitored by GC/MS. The brown liquid is extracted with ether (200 mL), washed with NaOH (100 mL of a 1 M solution), and vacuum distilled to remove excess aniline, leaving a dark brown solid. The solid is extracted into a minimum volume of hot methanol (ca. 160 mL) and cooled until crystallization occurs. The solid is collected on a sintered-glass frit and washed with cold methanol (2 x 20 mL) to afford white crystals. The filtrate is concentrated again to afford second and third crops. Yield 29.0 g (71%). 

Synthesis. The early PP plants used a slurry process adopted from polyethylene technology. An inert liquid hydrocarbon diluent, such as hexane, was stirred in an autoclave at temperatures and pressures sufficient to keep 10-20 percent of the propylene monomer concentrated in the liquid phase. The traditional catalyst system was the crystalline, violet form ofTiCl3 and A1C1(C2H5)2. Isotactic polymer particles that were formed remained in suspension and were removed as a 20-40 percent solid slurry while the atactic portion remained as a solution in the liquid hydrocarbon. The catalyst was deactivated and solubilized by adding HC1 and alcohol. The iPP was removed by centrifuging, filtration, or aqueous extraction, and the atactic portion was recovered by evaporation of the solvent. The first plants were inefficient because of low catalyst productivity and low crystalline yields. With some modifications to the catalyst system, basically the same process is in use today. 

Liquid samples are concentrated by evaporation or by separating the radionuclide of interest with processes such as filtration, precipitation, solvent extraction, ion exchange, sorption, and distillation. Solid samples are dried, ashed, compressed, or physically sorted. Gases can be sorbed, condensed, or compressed. Some steps may be performed at collection, others, in the laboratory. Recovery of the radionuclide of interest must be quantitative or at a previously determined fraction. 

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