Extractants influencing factors

Pfaab, G., and Jork, H. (1994). Application of AMD for the determination of pesticides in drinking water. Part 3. Solid phase extraction influencing factors. Acta Hydrochim. Hydrobiol. 22 216—223. 

Rutin extraction from buckwheat was optimally performed using between 50% and 60% ethanol with a 3-hr maceration (Kreft et al., 1999). Repeating the extraction two times was sufficient to extract most of the rutin. Lie et al. (2000) demonstrated the optimization of influencing factors such as extraction temperatures, extraction times, and solvent concentrations in a conventional extraction of dry powdered material of Hypericum perforatum. Applied extraction conditions caused variations to favor different components in the mixture. Higher extraction efficiency was achieved with moderately polar solvents to extract flavonoids such as rutin, isoquercitrin, and quercetin. The optimum extraction conditions for dry Hypericum perforatum leaf powder were determined as 44% to 69% ethanol in acetone with a 5.3- to 5.9-hr maceration at 55°C. 

The nature of the alkyl group had some influence on the stability of the amide extractants (a factor of 2 has been observed for high doses), and interest had meanwhile been aroused in the establishment of tendencies (191,192,194, 200). But the effect was strongly dependent on the diluent. 

Jacquel and co-workers [5] gave an overview of the various PHA extraction methods used, along with the respective purity and recovery, from 1978 to 2006. Furthermore, Roller and co-workers [3], and Kunasundari and Sudesh [27] gave a thorough review up to 2010. In this section, the subsequent updates on PHA recovery are discussed. Table 6.1 shows a summary of the recovery methods with respect to the influencing factors in each study reported from 2011 to 2015. 

The fact that the exponential term is the same as the one in the classical equation (9.16) reflects the assumption of both treatments that the free-energy profile is parabolic. Unlike the classical case, however, the pre-exponential term is influenced by A., and so the relation between ket and AG t (also that between ket and AG ) is different. Extracting the factor one can rearrange the equation into a form in which the pre-exponential term is not dependent on A ... 

In addition to extractive reaction, mass transfer is another important influence factor in the extraction process. When the mass transfer reached a stable state, the whole systems can keep a dynamic balance. The mass transfer happened between the aqueous phase and ILs, and the extraction kinetics interface of RE"" (n = 3 or 4) in ILs was shown in Fig. 5.6. Because the mass transfer rate also affects the extraction rate, the rate of RE " extraction is determined both by the chemical reaction rate and the mass transfer rate. Which one is more important in the two main factors is up to the experimental conditions. 

In spite of the importance of reaction prediction, only a few systems have been developed to tackle this problem, largely due to its complexity it demands a huge amount of work before a system is obtained that can make predictions of sufficient quality to be useful to a chemist. The most difficult task in the development of a system for the simulation of chemical reactions is the prediction of the course of chemical reactions. This can be achieved by using knowledge automatically extracted from reaction databases (see Section 10.3.1.2). Alternatively, explicit models of chemical reactivity will have to be included in a reaction simulation system. The modeling of chemical reactivity is a very complex task because so many factors can influence the course of a reaction (see Section 3.4). 

Gold (III) and palladium (II) are sorbed quantitatively on all studied sorbents, except for methyleneamine, from solutions 0,2-2 M HCI. The degree of platinum (IV) complex extraction substantially depends not only on the nature of sorbent functional groups, but also on geometrical parameters of the matrix. This factor influences gold (III) and palladium (II) soi ption to a lesser extent. 

Influence of the various factors in static conditions (concentration of heavy metals, both time of contact and ratio of solid and liquid phase, pH of medium) on solution of Pb(II), Cu(II), Cd(II) and Zn(II) from water solutions is studied and the optimal conditions of their extraction by organosilica sorbents modified by ions of Al(III) and Cu(II) are found. 

In order to illustrate the critical process parameters of SMB process validation, we will consider the separation of the racemic drug as described in Process design. The study represents the effect of the influence of feed concentration, number of plates and retention factor on the second eluting enantiomer. The simulation of the process for different values of feed concentration is performed and the variations of the extract and raffinate purities are shown in Fig. 10.10. 

Figure 10.12. Influence of retention factor of the more retained compound on extract and raffinate purity. Solid line without adjustment of the operating flow rates dotted lines with adjustment of the operating flow rates.

The choice of a satisfactory chelating agent for a particular separation should, of course, take all the above factors into account. The critical influence of pH on the solvent extraction of metal chelates is discussed in the following section. 

The wide distribution of chlorophylls throughout the plant kingdom facilitates the scrutiny of chlorophyll-rich vegetables for human nutrition with a view to their direct consumption. However, until now, little standardized information was available in the literature regarding the absolute total chlorophyll contents and the ratios of chlorophylls a and b in raw materials. The different analytical methods of extraction and quantification and the lack of data about moisture contents (that may vary considerably among varieties and preparations) can also influence the final contents of pigments. These factors have largely contributed to the discrepancies found in similar food samples. 

Considerable studies have been done on the effects of the most important chemical and physical factors involved in the degradation of anthocyanins (temperature, light, pH, SO2, metal, sugar, and oxygen) in model systems and food extracts. In addition, anthocyanin concentrations, its chemical structures, and media compositions are fundamental factors influencing stability. 

Updated infonnation regarding the extraction, purification, and functionalization of natural colors, with special focus on bioencapsulation procedures. The factors that specifically influence the stabihties of a whole range of natural colors, hydrophilic and lipophihc, for example, stabihty in the presence of low pH, fight, and heat, are considered along with solutions in given applications. 

Classical approaches to plant DNA isolation aim to produce large quantities of highly purified DNA. However, smaller quantities of crudely extracted plant DNA are often acceptable for PCR analysis. Another efficient method for preparation of plant DNA for PCR is a single-step protocol that involves heating a small amount of plant tissue in a simple solution. Several factors influence nucleic acid release from tissue salt, EDTA, pH, incubation time and temperature. These factors must be optimized for different sample substrates. EDTA in the sample solution binds the Mg + cofactor required by the Taq polymerase in the PCR, so the EDTA concentration in the solution, or the Mg + concentration in the PCR, must be carefully optimized. 

The separation of solids from liquids forms an important part of almost all front-end and back-end operations in hydrometallurgy. This is due to several reasons, including removal of the gangue or unleached fraction from the leached liquor the need for clarified liquors for ion exchange, solvent extraction, precipitation or other appropriate processing and the post-precipitation or post-crystallization recovery of valuable solids. Solid-liquid separation is influenced by many factors such as the concentration of the suspended solids the particle size distribution the composition the strength and clarity of the leach liquor and the methods of precipitation used. Some important points of the common methods of solid-liquid separation have been dealt with in Chapter 2. 

The efficacy and rate of the extraction process of additives from polymers are influenced by numerous factors including ... 

Principles and Characteristics Supercritical fluid extraction uses the principles of traditional LSE. Recently SFE has become a much studied means of analytical sample preparation, particularly for the removal of analytes of interest from solid matrices prior to chromatography. SFE has also been evaluated for its potential for extraction of in-polymer additives. In SFE three interrelated factors, solubility, diffusion and matrix, influence recovery. For successful extraction, the solute must be sufficiently soluble in the SCF. The timescale for diffusion/transport depends on the shape and dimensions of the matrix particles. Mass transfer from the polymer surface to the SCF extractant is very fast because of the high diffusivity in SCFs and the layer of stagnant SCF around the solid particles is very thin. Therefore, the rate-limiting step in SFE is either... 

Table 3.42 lists the main factors influencing optimisation of SPE. When considering a specific extraction problem, many different aspects influence column selection, including nature of the analytes and of the sample matrix degree of purity required nature of major contaminants in the sample and final analytical procedure. Reversed-phase sorbents have nonpolar functional groups and preferentially retain nonpolar compounds. Thus, for a nonpolar analyte, to remove polar interferences using a polar sorbent phase, the sample... 

Table 3.42 Factors influencing optimisation of solid-phase extraction...

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