Extraction references

Raw material Cellulose, % Hemicellulose, % Lignin, % Pectic material, % Extractives, % Reference... 

The last paragraph in this extract refers to work on the separation of uranium by ether extraction as a step toward obtaining a plutonium concentrate from a large sample of neutron-irradiated uranyl nitrate. 

In some cases we may benefit from using an external agent to carry out the desired separation through crystallization. Thus, in the case of isomeric and non-isomeric mixtures of close-boiling acidic or basic materials we may use a suitable base or acid to carry out dissociative extractive crystallization, akin to dissociative extraction referred to in Section 4.2.1. For instance, for a mixture of p- and m-cresol or p-cresol and 2,6-xylenol we may use a base like anhydrous piperazine to obtain a precipitate of relatively pure p-cresol salt of piperazine, which can then be filtered and subjected to recovery of piperazine for recycle. Similarly, we may add a substance which forms an adduct with the desired substance. 

For a full discussion of the methods that can be used to determine the stage requirements in liquid-liquid extraction refer to Treybal (1980), Perry et al. (1997) and Robbins (1997). 

The term solvent extraction refers to the distribntion of a solute between two immiscible liquid phases in contact with each other, i.e., a two-phase distribution of a solute. It can be described as a technique, resting on a strong scientific foundation. Scientists and engineers are concerned with the extent and dynamics of the distribution of different solutes—organic or inorganic—and its use scientifically and industrially for separation of solute mixtures. 

Table 4.2 gives a survey of the most common extraction processes. In general. Type I extraction refers to the distribution of nonelectrolytes, without (A) or with adduct former (B). Type n refers to extraction of (mainly organic) acids. Type III to the extraction of metal complexes, and Type IV to the special (but common) nse of solvent extraction for evaluation of formation constants... 

This time capsule also contained the tablets on which the commandments were written, a square, golden table inlaid with fourteen precious stones, and a box inscribed with the seven names of God. Forman cited a variety of sources, including Josephus, Augustine, and the popular fifteenth-century world chronicle, Werner Rolevinck s Fasciculus temporunr, perhaps he consulted these texts himself or extracted references to them from the standard histories that prefaced magical and alchemical texts. ... 

Nondestructive solvent extraction of coal is the extraction of soluble constituents from coal under conditions where thermal decomposition does not occur. On the other hand, solvolysis (destructive solvent extraction) refers to the action of solvents on coal at temperatures at which the coal substance decomposes and in practice relates in particular to extraction at temperatures between 300 and 400°C (572 and 752°F). In the present context (i.e., the solvents extraction of coal), the solvent power of the extracting liquid appears to be determined solely by the ability of the solvent to alter the coal physically (by swelling). In this respect, the most effective solvents are aromatics, phenol derivatives, naphthol derivatives, anthracene, and phenanthrene. 

The term Third-Phase Formation in solvent extraction refers to a phenomenon in which the organic phase splits into two phases (126). One of the two phases is diluent rich, whereas the other is rich in extractant and also contains the metal solvate. Third-... 

We have at our disposal a large number of parameters known both from reference literature or experience. We should define a unique response or optimization parameter, and in case this does not work we should make an attempt with a general response. Since extraction refers to processes of separating phases, they are defined by several parameters-technologically, thermodynamically, economically, statistically, etc. Important and essential properties of the separation process are degree of separation of the required component, economy per finished product and quality of product. Growth of any of these parameters brings about a fall in others. 

Sequential extraction Reference material(s) Elements determined Reference... 

Evening primrose (Oenothera biennis L.), a biennial plant belonging to the Ona-graceae family, is considered a weed native to North America. It is cultivated in a number of countries on account of the nutritional and pharmaceutical properties of the oil which is in constant demand (Carter, 1988). The oil extracted, referred to as evening primrose oil (EPO), is a good source of GLA. Unlike commercial oilseeds, evening primrose does not produce a high yield of seeds, but is a preferred source of GLA as it does not contain any ALA. 

Acidic and Neutral Extract Reference Solutions. Prepare solutions in chloroform of authentic samples of drugs as indicated in Table 1, each drug being at a concentration of 1 mg/ml. Method. Divide a TLC plate (silica gel G, 250 iLim) into 8 equal columns by scoring lines with a spatula, and draw a horizontal line 10 cm from the origin, ply 10- li1 aliquots ofthe reference solutions and 25-p, aliquots of the sample extract to the columns on the plate in die sequence shown in Table 1. Evaporation of the spots can be hastened by the use of a cold air blower. 

Generally, the term micro extraction refers to an extraction technique where the volume of the extracting phase is very small in relation to the volume of the sample, and the extraction of the analytes is not exhaustive. The fraction of the initial analyte extracted depends on the partitioning of the analyte between the sample matrix and the extraction phase. The higher the affinity of the analyte for the extraction phase, the greater the amount of analyte is extracted. Once sufficient extraction time has been reached and equilibrium has been established, further increases in extraction time do not affect the amount of analyte extracted. 

Fig. 12.2. Values for mass fractions of FI 18 in a fly ash extract reference material, expressed in pg kg. Results obtained by Lab. 05 correspond to the use of a DB Dioxin column, which allows a better resolution for FI 18/Fl 19.

The modified Thiele-Geddes method described in Section 13.2 is adapted here to liquid-liquid extraction. Reference is made to the steps described in that method. 

Part If A of the Environmental Protection Act 1990 requires Local Authorities to identify contaminated land. Circular 2/20007 provides Local Authorities with advice on how to determine that there is a significant possibility of significant harm being caused . The following extracts refer to specific indicated sections ... 

The use of supercritical CO2 to extract AR from cereal material was only recently presented (49). Pure supercritical CO2 was not able to extract AR even at pressures as high as 35 MPa and SS C. This result was attributed to the amphiphilic character of the AR and the non polar character of the supercritical CO2. With the addition of 10% of ethanol or methanol, it was possible to obtain extracts even at near the critical pressure (8 MPa). The optimal pressure was determined to be 3SMPa at S5°C when ethanol or methanol acted as co-solvent. The co-solvent was added as 10%wAv of the CO2. The CO2 flow was kept constant at Sg/min during the experiments. A comparison of the supercritical CO2 extraction with die addition of ethanol and classical extraction methods was made. For the classical method, pure acetone extraction at O.IMPa and 20°C was used. Between 15 and 30 MPa at 55°C, 8 to 80%w/w higher yields of AR crude extracts for the extraction with supercritical CO2 with co-solvents were obtained than for pure acetone extraction (refer to figure 2). However, the HPLC analysis of the extracts showed similar composition (49). 

Powdered drug.s are used for extraction e.g. medium-fine powder corresponds to mesh size 300. Sample weights quoted for drug extraction refer to the dried drug. 

K. Kersters and J. de Ley, Enzymic Tests with Resting Cells and Cell-Free Extracts , reference 2, Ch. 2, pp. 33-52. 

Much of the research on garcinia is focused on a standardized extract referred to as HCA-SX, a garcinia extract that contains 60% of the compound hydroxycitric acid (HCA) (Soni et al. 2004). Garcinia fruit rind naturally contains approximately 16 to 26% HCA (Antony et al. 1998 Jayaprakasha and Sakariah 1998). 

This author was astonished one day back in the 1980s when he obtained a sample of an aqueous phase from a Superfund waste site that had been extracted (refer to the discussions of LLE in Chapter 3) with methylene chloride. The remaining extracted aqueous phase was sent to waste. The organic extract was analyzed using EPA Method 8270. This is a C-GC-MS(MSD) determinative method that separates, identifies, and... 

Table 9.4.3 and Scheme 9.4.6 show that contents as well as structure of the extractives can vary greatly between the wood species. Furthermore, there are large differences between wood parts of, for example, sapwood and heartwood (see below) or between wood and bark. Therefore, it is very difficult to briefly describe extractives and the reader is referred to the literature. " Since the name of the extractives refers to their isolation method, it follows that the term extractives includes non-specifically all substances which can be extracted from the wood using solvents with most different polarities. Hence the term extractives must be considered in a much differentiated manner, as... 

Normal-phase solid-phase extraction refers to the mechanism by which the analyte is adsorbed onto the polar surface of sorbent from a nonpolar solvent. The mechanism of interaction between the analyte and sorbent is a polar interaction, such as hydrogen bonding, dipole-dipole interaction, n-K interaction, and induced dipole-dipole interaction. The sorbents widely used in normal-phase SPE are silica, alumina, and magnesium silicate (Florisil), and the siUca chemically modified with polar groups like amino, cyano, or dioLThe samples for normal-phase SPE are typically dissolved in hexane or isooctane. Step elution with solvents of increasing polarity allows the separation into fractions on the basis of difference in polarity. 

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