Direct solvent extraction

To surpass the above limitations, new developments have recently enabled access to all of the metallofiillerenes generated by the arc process, not just M C82 (Bolskar and Alford, 2003 Bolskar et al., 2003). Other metallofiillerenes such as M C60, M C70, and M C74 are more prevalent in the arc products, but are not as soluble as M C82 (Diener and Alford, 1998). A recent study of arc-generated Gd metallofiillerenes found that soluble Gd C82 comprises only about 10% of the total metallofullerene product, with the majority, 90%, being other insoluble Gd C2n (Raebiger and Bolskar, 2008). To access the total Gd metallofullerene content, processes other than just arc soot extraction with solvents were implemented. Sublimation effectively removed all fullerenes and metallofiillerenes from the arc soot, leaving the non-fullerene amorphous carbon behind. Direct solvent extraction... 

Carotenoids A large number of solvents have been used for extraction of carotenoids from vegetables matrices, such as acetone, tetrahydrofuran, n-hexane, pentane, ethanol, methanol, chloroform [427-431], or solvent mixtures such as dichloromethane/methanol, tetrahydrofuran/methanol, -hexane/acetone, or toluene or ethyl acetate [424,432-435], SPE has been used as an additional purification step by some authors [422,426], Supercritical fluid extraction (SEE) has been widely used, as an alternative method, also adding CO2 modifiers (such as methanol, ethanol, -hexane, water, methylene chloride) to increase extraction efficiency [436-438], In addition, saponification can be carried out, but a loss of the total carotenoid content has been observed and, furthermore, direct solvent extraction has been proved to be a valid alternative [439],... 

Methods of extracting the fat-soluble vitamin from food matrices include alkaline hydrolysis, enzymatic hydrolysis, alcoholysis, direct solvent extraction, and supercritical fluid extraction of the total lipid component. 

Current multiresidue methods for alkaloids typically involve extraction with a polar solvent such as ethanol, evaporation to remove the solvent, and a series of acid/base liquid-liquid partition steps for cleanup. An alternative method is extraction with aqueous acid followed by alkaliniza-tion and extraction into organic solvent or by the use of SPE columns. Direct solvent extraction... 

Miscellaneous organics Miscellaneous solvents Comparison of direct solvent extraction GLC and headspace analysis [474]... 

Direct solvent extraction techniques are widely used and range from very simple procedures where solvent and sample are mixed and dried to the use of supercritical CO2 and pressure chambers. The efficiency of the technique is influenced greatly by the choice of solvent. 

A general flow sheet for direct solvent extraction of many row crop oilseeds is shown in Fig. 34.8. Initial quality of the seed, and its preparation for extraction, have the most effect on yield of extracted oil, subsequent required refinery operations, and yields of (saleable) neutral oil. Freshly harvested seed should be cleaned of trash, which may become ignited during drying, or harbor moisture that accelerates seed heating in storage. Oils of most good quality, dry, row crop... 

Introduction of the expander has enabled extraction plants to handle additional seed species, with purchase of only minimal cleaning and dehulling equipment where needed. Prepress-solvent extraction facilities are being replaced by expander-direct solvent extraction equipment, leaving two basic extraction processes in modern large volume oilseed extraction plants expander-direct solvent extraction, and hard press for applications... 

Rapid gas chromatographic screening can be carried out using direct solvent extraction of small volumes of samples. Extractions are performed in small disposable test-tubes, and no transfer or evaporation of solvent is involved, so that drugs are not lost in the procedure. Accurate micro-pipetting and the use of internal standards enables quantification of drugs detected in serum or plasma samples. 

Direct solvent extraction and examination by TLC and immunoassay Confirmation and quantification by UV, GC, HPLC, MS... 

Direct solvent extraction before or after acid or enzymatic digestion has almost superseded die classic protein precipitation methods. Due to die more sensitive detection methods of gas chromatography and mass spectrometry, much smaller amounts of tissue can be processed. Consequently, any emulsion problems that arise are more easily resolved than in the past when several hundred grams of liver and large volumes of solvent were required. 

The volumes of water used and any dilutions necessary for the ultraviolet examination must be noted in order to give a quantitative estimate of any drug present. Apart from die small amount used for TEC, the bulk of die extract is still available should analysis by gas chromatography or mass spechometry be required. Direct solvent extraction can be applied to the exhacts, and dilutions used for ultraviolet spectrophotometric analysis. This may also be necessary if die syringe is heavily blood-stained. It is important to remember that some of the drugs encountered in syringes are susceptible to alkaline... 

Two methods are described, one using direct solvent extraction, and the other a solid-liquid extraction. 

The use of aqueous acid or alkali to elute the compound from the thin-layer plate or paper chromatogram, followed by solvent extraction of the aqueous solution, is more efficient than direct solvent extraction of tiie adsorbent... 

Cottonseed 19 Hard pressing or prepressing or direct solvent extraction... 

For this purification process, the crude miscella source may be from (1) the preevaporator of a direct-solvent extraction plant, (2) a blend of prepressed crude oil and solvent-extracted miscella from the press-cake, or (3) a reconstituted blend of crude oil with solvent. In the process, a mixture of approximately 40% to 58% oil in solvent is heated or cooled to 104°F (40°C) and filtered to remove meal, scale, and other insoluble impurities. Two solvents that have been used commercially for miscella refining are hexane and acetone. 

Direct solvent extraction is the most widely used oil-recovery method for soybeans, but it also requires considerable capital and large scale to compete. In actual practice, solvent extraction is used to crush over 98% of the soybean processed in the United States. Process flow diagrams are shown in Figures 3 and 4. Most soybean solvent-extraction plants process more than 2,500 MT/day (Figure 5), and some are capable of processing as much as 5,000 MT/day (especially newly constructed plants in Brazil). Direct-solvent-extraction plants smaller than 1,000 MT/day have difficulty competing in the United States. At various times, soybeans have been extracted commercially with petroleum distillate fractions that resemble gasoline, acetone, carbon disulfide, ethanol, trichloroethylene, and even water. 

Figure 3. Process flow diagram for direct solvent-extracting soybeans.

Figure 4. Depiction of equipment and process flow diagram for direct solvent-extracting soybeans (courtesy of French Oil Mill Machinery Co., Piqua, OH).

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