Solid extractants stability

Figure 14.5. Fatty acids patterns of soils under long-term monoculture, (a) Lipid extract of soil under maize, unfertilized, after derivatization with tetramethylammonium hydroxide determined by conventional gas chromatography/mass spectrometry (GC/MS) in comparison to direct, in-source pyrolysis-field ionization mass spectrometry (Py-FIMS) without derivatization (Jandl et al., unpublished), (b) Py-FIMS of lipid extract of soil under rye, farmyard manure (FYM) treatment, compared to solid extraction residue, both directly measured without derivatization. Reprinted from Marschner, B., Brodowski, S., Dreves, A., et al. (2008). How relevant is recalcitrance for the stabilization of organic matter in soils Journal of Plant Nutrition and Soil Science 171, 91-110, with permission from Wiley-VCH.

Castillo, M., D. Puig, and D. Barcelo. 1997. Determination of priority phenolic compounds in water and industrial effluents by polymeric liquid-solid extraction cartridges using automated sample preparation with extraction columns and liquid chromatography Use of liquid-sohd extraction cartridges for stabilization of phenols. J. Chromatogr. A 778 301-311. 

Appropriate SPE sorbent selection is critical to obtaining efficient SPE recovery of semivolatile organics from liquids. Henry [58] notes that an SPE sorbent must be able to sorb rapidly and reproducibly, defined quantities of sample components of interest. Fritz [73] states that successful SPE has two major requirements (1) a high, reproducible percentage of the analytical solutes must be taken up by the solid extractant and (2) the solutes must then be easily and completely eluted from the solid particles. The sorption process must be reversible. In addition to reversible sorption, SPE sorbents should be porous with large surface areas, be free of leachable impurities, exhibit stability toward the sample matrix and the elution solvents, and have good surface contact with the sample solution [68,73],... 

Solid extractants made of functional ligands and inorganic supports have attracted much attention because of their mechanical strength, thermal stability, wide range of particle size, and well-dehned pore structure of these materials. In particular, the well-defined pore structure provides a good environment for diffusion of metal ions in the solid matrix. 

Agar occurs as a cell-wall constituent of the red marine algae Rho ophyceae, from which it is extracted by hot water, and marketed as a dry powder, flakes, or strips. It dissolves in hot water and sets on cooling to a jelly at a concentration as low as 0-5%. Its chief uses are as a solid medium for cultivating micro-organisms, as a thickener, emulsion stabilizer in the food industry and as a laxative. 

Chlorofonn is too non-polar to dissolve the phenolic compounds under study, but it dissolves many of the monoterpenes, at least to some extent. Because the solubility of some monoterpenes into chloroform was low, different solvent/ solid ratios were tested. These were 50,20,10 and 5 1/kg of dry phloem. The extracts were bright yellow and the strongest colour was with the smallest solvent/solid ratio (51/kg). The colour of the solvent indicated that the solubility of the extractable compounds was not restricting the reaction even with the smallest solvent volume. The taste of the dry samples was evaluated by comparing them to the original phloem sample. The results showed that the mildest taste was in the phloem extracted with a solvent/solid ratio of 50 1/kg and 20 1/kg also had some effect on the taste. The taste of the chloroform-extracted phloem was stabile and it was the same after a week. 

Betalains are vacuolar plant pigments. Hence their hydrophilic nature is comprehensible. Although they are slightly soluble in ethanol and methanol, water is the best snited solvent both for stability and solnbility reasons. In contrast to the antho-cyanins, the betalains are even more polar as can be demonstrated by shorter retention times in RP-HPLC and lower solubilities in alcoholic solutions. The varying polarities may also be beneficially used to separate anthocyanins from betalains on an RP-18 solid-phase extraction cartridge (Stintzing, unpublished data). 

The use of ethyl acetate was suggested by Oszmianski and Lee (1990) to wash out phenolics other than anthocyanins. Finally, a relatively pure anthocyanin extract can be removed from the colnmn with acidified methanol (0.1% HCl). Anthocyanin extracts can be enriched in this way by use of solid phase purification, which is especially helpful for diluted samples such as biological samples. Two factors in the nse of these purification techniques are the stability of anthocyanins to the conditions nsed and the ease of anthocyanin recovery from the column. ... 

For preparing lakes, a solution of aluminium sulfate (or chloride) is mixed with sodium carbonate, forming fresh alumina Al(OH)3. The colorant is then added and adsorbed on the surface of alumina. Usually the content of colorant in the lake ranges from 10 to 40%." The product is filtered, washed with water, dried, and milled. The product is allowed to contain unreacted alumina but must not contain more than 0.5% HCl-insoluble matter and not more than 0.2 % ether-extractable matter. - Lakes are insoluble in most solvents used for pure dyes, and they have high opacity and better stability to light and heat. Lakes impart their color by dispersion of solid particles in the food. The coloring properties of lakes depend on particles, crystal structures, concentrations of dye, etc. 

The functional viscosity of the gums is also widely used to suspend solids in an aqueous medium. This can be considered as solid phase emulsification. As little as 0.03 to 0.05% of Irish moss extract will retain cocoa solids in suspension in chocolate sirup this colloid is specific for the purpose, even in the absence of milk solids. Many chocolate-flavored fountain sirups are stabilized in this manner, which prevents the cocoa from settling and packing at the bottom of the container. 

The given structure shows two molecules of TTA to have reacted with a cobalt ion to form the cobalt-TTA complex, in which the cobalt atom forms a valence bond solid lines) with one, and a coordinate bond (broken lines) with the other, oxygen atom of each TTA molecule. Thus, in the cobalt-TTA complex there is a six-membered ring formed by each TTA molecule with the cobalt atom. Metal chelate complexes of this type have good stability, they are nonpolar and soluble in the organic phase. The usefulness of the chelating extractants in solvent extraction is therefore obvious. 

Oligomerization of nucleobases can be advantageous to reinforce the H-bonding supramolecular motifs when supramacromolecular polymers are desired. Moreover the different interconverting outputs that may form by oligomerization define a dynamic polyfunctional diversity which may be extracted selectively under the intrinsic stability of the system or by interaction with external factors by polymerization in the solid state. 

Inman, B.L. et al. 2006. Solid phase extraction as a faster alternative to HPLC Application to MS analysis of metabolic stability samples. J. Pharm. Sci. 2006, Nov. 8, Epub., ahead of print. 

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