Conditions for extraction

Optimisation of these conditions is a most difficult step and of great concern in SFE, since it has a direct impact on the added value of the technique. Optimisation of the experimental conditions for extraction... 

Chau et al. [19] have described the optimum conditions for extraction of alkyllead compounds from sediments originating in non-saline waters and in saline waters [16]. Analyses of some environmental samples revealed for the... 

Before the extraction procedure may commence, the sample must be prepared in such a way that it is in a condition for extraction of the analyte(s). For analyzing sulfonamide residues in liquid samples such as milk, a pretreatment dilution step with water prior to direct fluorometric detection may be required (207). Dilution of milk with aqueous buffer (208) or sodium chloride solution (209) prior to sample cleanup has also been reported. For the analysis of honey a simple dissolution of the sample in water (210, 211) or aqueous buffer (212) is generally required. Semisolid samples such as muscle, kidney, and liver, require, however, more intensive sample pretreatment. The analyte(s) must be exposed to extracting solvents to ensure maximum extraction. The most popular approach for tissue break-up is through use of a mincing and/or homogenizing apparatus. Lyophilization (freeze-drying) of swine kidney has been carried out prior to supercritical-fluid extraction of trimethoprim residues (213). 

For the energy- and cost-calculation of the HPE-process a program has been developed, allowing the determination of the various cycle processes under selected conditions for extraction and separation. In principle, the cycle is either in the pump- or in the compressormode. 

FIGURE 35 Emulsified liquid membrane separation mechanisms (A) selective permeation (B) chemical reaction inside emulsion droplet and (C) chemical conversion in liquid membrane and further conversion inside droplet. Both (B) and (C) provide quasi-infinite sink conditions for extraction from the feed solution. 

Calculations of treatment costs for supercritical soil remediation were made with a computer model that evaluates the capital and operating costs depending on plant capacity, carbon dioxide conditions for extraction and separation, operating conditions, soil transport and pretreatment and other boundary conditions like maintenance, depreciation or insurance. Some additional important parameters for the plant design are given in table 1. 

In some instances the carrier of the guest plays the role of emulsifier. For example, alcohols and lower fatty acids or their esters are used in the formation of fat-starch complexes.676 In this case, conditions for preparation of complexes resemble conditions for extraction, and unexpected results can accompany both processes. For example, it has been shown that extraction of lipids with 1-propanol from their surface complex with oat starch produced a helical lipid-starch complex that was absent prior to extraction.677... 

The higher concentration reported by Napoli et al. (22) may be due to hydrolysis of the glucuronide metabolite since retinoyl glucuronide is hydrolyzed by acid or base to retinoic acid (33.341. The extraction procedure of Napoli et al. (22) utilized 2N HC1 which could potentially convert most of the retinoyl glucuronide to retinoic acid. Therefore, the concentration of all trans retinoic acid as reported by this assay could represent the sum of these two retinoids, and not that of the free acid (22). Our assay uses less harsh acidic conditions for extraction which should prevent hydrolysis of the glucuronide, resulting in a lower plasma concentration of the all trans isomer as reported by Napoli et al. 22). 

An introductory chapter on the furoquinoline alkaloids with excellent coverage and leading references to the literature has been published as part of a general volume on alkaloids.1 A detailed chromatographic analysis of quinoline alkaloids in liquid-liquid systems with buffered aqueous phase and a polarographic method for the determination of dubinidine from Haplophyllum foliosum have been reported.2 From a pH-R f relationship, the optimum conditions for extraction and chromatography were developed.20... 

The yield of cranberry seed oil via Soxhiet extraction was 23.1% and via SFE was 21.4%. These results are similar to the lipid composition (23.3%) of cranberry seed oil obtained by Croteau and Fogerson. The optimized SFE conditions for extracting fatty acids from cranberry seeds were CO2 pressure = 450 atm, extraction temperature = 45 C, CO2 flow rate = ImL/min, and extraction time = 90min. SFE showed better RSD s, comparable recoveries, and... 

Solids (TDS), Organic Dissolved Solids (ODS). For elemental content determination of the water samples Emission Spectroscopy was made and for the quantitative determination of significant metals - Atomic Absorption Spectroscopy ( Perkin Elmer-323 ) and UV-spectroscopy ( Perkin Elmer-5000 ). Based on the preliminary experiments (Koumanova et al., 1983) the following optimum conditions for extraction of the hydrocarbons from polluted with oily products water samples were established an adsorption on natural sorbent, followed by an eluation with methylene chloride and additional extraction with methylene chloride at pH 2. The concentrated extract was analyzed with Gas Chromatography and Mass Spectrometry for identification and quantitative determination of the extracted hydrocarbons. 

The last process that can change the flavor, odor, color, nutritional attributes, and the oxidative stability of soybean oil is deodorization. If the conditions for extraction and crude oil processing are satisfactory, the result is a tasteless, odorless, light-colored oil, free from peroxides and other contaminants. Storage, handling, and packaging of the purified oil must protect the achieved quality prior to use by the consumer or use in... 

The first example is the application of two-stage fractional extraction to selectively remove components from fennel (J). The first extraction stage operates under subcritical temperature conditions for extraction, i.e. 130 BAR and 30 C. Approximately 9% of the feed material is removed and the resulting extract is over 50% essential oil. The residue in the extractor vessel is then extracted a second time using supercritical conditions, i.e. 300 BAR... 

The conditions for extracting metal ions from hydrochloric acid solution into ethyl ether as ion-association complexes are shown in Figure 20.7. 

The data (1 to 9% extracted hair lipid) represent total matter extracted from hair clippings of individual men and women. Although the conditions for extraction can influence the amount of matter extracted from hair [138], the values here represent approximate maxima and serve to indicate the variation in the amount of extractable material from hair among individuals. Presumably, the principal material in these extracts is derived from sebum and consists primarily of free fatty acids and neutral fat (esters, waxes, hydrocarbons, and alcohols). Gloor [137] classifies the different components of sebum into six convenient groups free fatty acids (FFA), triglycerides (TG), free cholesterol (C), cholesterol and wax esters (C WE), paraffins (P), and squalene (S). 

Merkle, J.A. and Larick, D.K., Conditions for extraction and concentration of beef fat volatiles with supercritical carbon dioxide, J. Food ScL, 59,478,1994. 

Zhen CG, Guo YY, Zhang XC, Miao J, Shi WP. Optimisation of conditions for extracting pesticidal alkaloids from Cynanchum komarovii (Maxim.). Nat Prod Res 2013 27(l) 23-7. 

Before analysis by HPLC can be performed, an initial sample purification is often necessary. Various purification methods for leukotrienes have been described in the literature. Depending on the type and size of the sample, and whether a total analysis is intended or if only certain components should be analyzed, different procedures can be used. The cysteinyl-containing leukotrienes are somewhat acid labile and require mild conditions for extraction and purification. A first extraction of leukotrienes from biological samples can be achieved by adsorption to some resin, e.g. Amberlite XAD-8 or XAD-7, at slightly acid or neutral pH [64,91,112,215] or adsorption to charcoal [75,118] or to Sephadex LH-20 [69]. Mild extraction into organic solvents at low temperature has also been used for cysteinyl-containing leukotrienes [119], although this method has preferably been used at a later step in the purification procedure for these compounds [75],... 

Coal macromolecules are associated (interlocked and intermeshed) with each other so strongly that it generally requires stronger conditions for extraction or solubilization of more than 10%-20% of coal. Extraction of coal in an organic solvent is an essential requirement for the conversion of coal to value-added fuels and chemicals without a significant loss in original coal constitution and its energy. Such a concept require that the coal be treated with a solvent under conditions such that the coal is decomposed into smaller molecular entities— the process is known as solvolysis, which refers to the action of solvents on coal at tanperatures at which the coal substance decomposes and in practice relates in particular to extraction at tanperatures between 200°C and 400°C (390 F and 750°F). This concept is often used as a means of coal liquefaction (Chapters 18 and 19). 

Although during the first years of development of sequential extraction almost every researcher had his own sequence, made on the basis of more or less free selection of extraction instruments and order of their use, recently there has been relative unification of applied models, and hence there is a possibility of appropriate comparison of findings made by various authors. Since selectivity of certain extractors is already relatively well known, and so are the effects of secondary reactions, re-adsorption and other obstructing occurrences, the authors seldom use - in essence inadequate - notions such as exchangeable phase , easily reducible phase , etc. but more frequently use notions such as ammonium-acetate phase , hydroxylamine phase , etc. Therefore, isolated metal fractions are ascribed to applied extraction instruments, naturally with clearly defined conditions for extraction, which have been more or less standardized for each extraction level. In order to ascribe fractions of heavy metals, defined in this manner, to a certain substrate, one has to know to what extent were the most widely spread substrates susceptible to the effect (breakdown, i.e. dissolving) of applied extraction instruments. 

Specht, W., Pelz, S., Gilsbach, W. (1995) Gas-chromatographic determination of pesticide residues after clean-up by gel-permeation chromatography and mini-sihca gel-column chromatography. 6. Commimication replacement of dichloromethane by ethyl acetate/ cyclohexane in hquid-liquid partition and simplified conditions for extraction and hquid-liquid partition. 

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