Mild Extractants

FIGURE 37.5 General refining techniques for production of distillate aromatic extract (DAE), mild extraction solvate (MES), and treated distillate aromatic extract (TDAE). (From Joona, M., High-aromatic tire extender oils implications and future, ITEC, OH, 2004.)... 

Principles and Characteristics A good extraction method, in addition to quantitative recoveries, ensures a high degree of selectivity. The demands for quantitative and selective extraction are difficult to meet simultaneously. Quantitative extraction with recoveries being independent of the matrix requires a strong extraction fluid. On the other hand, selective extraction is usually associated with fairly mild extraction conditions where only the components of interest are dissolved... 

Mild extraction was also found to be effective in the analysis of extracts of Flaveria haumanii, l in which quercetin, kaempferol, isorhamnetin as well as their glycosides and sulfate esters were identified. The obtained results were useful in the identification of the colourants from fibres from pre-Columbian Andean textiles extracted with the use of water-methanol solution with formic or hydrochloric acid. The components of each extract were separated on a reversed phase HPLC column and the eluates were monitored at... 

X. Zhang and R.A. Laursen, Development of mild extraction methods for the analysis of natural dyes in textiles of historical interest using LC diode array detector MS, Anal. Chem., 77, 2022 2025 (2005). 

Petersen, M. A., Poll, L., Larsen, L. M. (1998). Comparison of volatiles in raw and boiled potatoes using a mild extraction technique combined with GC odour profiling and GC-MS. Food Chem., 61,461 66. 

Thus, the fat globules are surrounded, at least initially, by a membrane typical of eukaryotic cells. Membranes are a conspicuous feature of all cells and may represent 80% of the dry weight of some cells. They serve as barriers separating aqueous compartments with different solute composition and as the structural base on which many enzymes and transport systems are located. Although there is considerable variation, the typical composition of membranes is about 40% lipid and 60% protein. The lipids are mostly polar (nearly all the polar lipids in cells are located in the membranes), principally phospholipids and cholesterol in varying proportions. Membranes contain several proteins, perhaps up to 100 in complex membranes. Some of the proteins, referred to as extrinsic or peripheral, are loosely attached to the membrane surface and are easily removed by mild extraction procedures. The intrinsic or integral proteins, about 70% of the total protein, are tightly bound to the lipid portion and are removed only by severe treatment, e.g. by SDS or urea. 

An earlier report from this laboratory (7) noted that in a series of mildly extracted mordenites, the hexane cracking activity in a continuous-flow test went through a marked maximum with increasing severity of extraction, while the f-butane to n-butane ratio continuously increased. The activity and product distribution were measured after 10 min on stream. Since catalyst deactivation was rapid, it was not possible to... 

In general, volatile components can be extracted from the dried raw materials under conditions close to the critical point of carbon dioxide. Temperatures should be within the range of 32 to 60°C. However, some heat-sensitive components may decompose, even below this range. Extraction pressures should be between 74 and 120 bar, since at higher pressures the increased solvent power of CO2 also increases the solubility of unwanted components. The yields obtained by SFE are very similar to those found by steam distillation. However, even under mild extraction conditions, some small amount of cuticular waxes is co-extracted with the volatiles. The major constituents of the waxes are -paraffins, ranging from C25 to... 

Accurate determination of lipids in foods is required for nutritional labeling, certification, or for evaluation of standard of identity and uniformity, as well as examination of their effects on functional and nutritional properties of foods. Following lipid extraction and precise quantitative analysis, lipids so obtained may be used for analysis of other lipid characteristics and properties provided that nondestructive and mild extraction procedures are employed that retain the integrity of lipids. Thus, determination of lipid classes, fatty acid composition (unit du), and oxidative state of lipids (Chapter D2), amongst others, may be pursued following the extraction process. 

Applying mild extraction methods to the mycelium of an ergo-cristine producing Claviceps purpurea strain, an unstable peptide alkaloid of a new type was recently detected (17). Its physical data and chemical transformations contributed to the elucidation of its structure. The fast methanolysis of the new alkaloid led to the well-known N-lysergyl-L-valine methyl ester (18) and L-phenylalanine-D-proline lactam. An amino acid analysis showed the presence of one mole each of valine, phenylalanine, and proline. Thus the new alkaloid has been characterized as iV-[AT-(d-lysergyl)-L-valyl]-L-phenylalanyl-D-proline lactam (18 C35H39N504 mp 235° [a]D +5° in chloroform). 

When extracting chondroitin sulfate from salmon head cartilage, collagen inevitably accompanies it. In this extraction process, from a pharmaceutical point of view, collagen is considered as an impurity. This is a kind of contradiction because if we administrate chondroitin sulfate and collagen simultaneously, the result will be beneficial and effective. Most marine bioresources contain many health beneficial compounds even in the same tissues. For this reason, we should design sequential extraction processes of those useful compounds from the most value added to the poorly valued compounds. For example, the first step for pharmaceutical use should be the mild extraction of compounds. And the final step should extract materials for fertilizers. 

The results of sequential leaching experiments and the bioaccumulation studies reveal a selective assimilation of certain chemical forms of some trace metals by molluscs. There seems to be a relationship between seawater-soluble chromium levels and accumulation of the element in the kidneys of exposed bivalves. Particulate forms of chromium, while present in the digestive glands, do not appear to have been assimilated by the organisms, even though much of the total chromium was dissolved by a relatively mild extractant -25% acetic acid. Thus, an estimation of the bioavailability of particulate metals based on their solubility in dilute acetic acid can be erroneously high, at least for herbivorous filter feeders. 

CO2 density on extraction of all-ira 5-lycopene from tomatoes and found the greatest yield at the highest density (0.90 g/mL) tested. However, while SFE is a relatively mild extraction technique, it is still necessary to consider the effect of extraction conditions on carotenoid stability to minimize the formation of isomer artifacts (Spanos et ah, 1993). 

Mechanism (1) is particularly important in peat and other organic-rich sediments, where clay and metal complexes are present in very low amounts in relation to the humus component. A typical example of humic substances bound by polyvalent complexes (item 2) is the Spodosol. These soils have developed under climatic and biologic conditions that have resulted in the mobilization and transport of considerable amounts of iron, aluminum, and organic matter into the B horizon. This illuvial horizon is a rich source of fulvic acids, which are readily separated from the sesquioxides by mild extractants. 

Desorption is often a slower process than adsorption, and a phenomenon called aging prevents a total extraction by water or mild extraction solutions (methanohwater (1 1 v/v), ammonium acetate, etc.) to extract the pesticide completely from soil, even if it is sufficiently soluble in the solvent. The amount that is nonextractable increases over time. The reason for this has not yet been settled. One theory is that the soil has many extremely small pores (nanopores). In the course of time the adsorbed molecules diffuse into such pores, where they are not easily extracted and have a low and decreasing bioavailability. An alternative theory is that they are first adsorbed to some easily available low-affinity binding sites and over time jump over to high-affinity binding sites. 

For less soluble contaminants like PAHs and PCBs, it is not possible to measure pore water concentrations. Chemical availability has to be measured with a method that extracts a certain part from soil. Methods are available, such as a mild extraction for a short period of time. Relation with effects have been empirically established (certain strength and certain time). Methods are easy and cheap, but valid only after establishing the empirical relationship. Other methods are based on a strong adsorbent and stimulate the diffusion from the solid phase into the water phase and on to the adsorbent. This process is easier to understand (based on equilibrium between soil and water), but is also based on empirical relationships (Reid etal. 2000). 

In Colombian green coffee, Boosfeld et al. (1994) and Boosfeld and Vitzthum (1995) elucidated the structure of two pairs of unsaturated aldehydes, (E,E)-2,4- and (2F,4Z)-2,4-nonadienal as well as (E,E)-2,4- and (2 , 4Z)-2,4-decadienal, probably generated via autoxidation of unsaturated fatty acids and contributing particularly to the typical green-coffee odor. The products were identified by mass spectrometry, GC-FTIR and NMR spectroscopy. The authors used particularly mild extraction techniques in order to avoid artifact formation and isomerization of the conjugated double bonds. The sensory impressions of these aldehydes at the sniffing port varied from metallic, fried, and flowery to oily notes. 

For biological evaluation larger quantities of component phenols and their constituents may be required and where different components such as alkylresorcinols and anacardic acids co-occur, an initial solvent separation may prove desirable. Mild extraction methods, such as supercritical fluid extraction with carbon dioxide, [1,219,220], followed by phase separation [221], preparative TLC [222], or column chromatography [223] may be valuable for complex mixtures. 

---