Matrix dehydration

Parks OW, Lightfield AR, Maxwell RJ. Effect of sample matrix dehydration during supercritical-fluid extraction on the recoveries of drug residues from fortified chicken liver. J Chromatogr Sci 1995 33 654-657. 

EuSe is formed in the in situ reaction of EUCI3 (from a matrix dehydration procedure) with dry H2Se in a vitreous carbon boat at ca. 1025 K in 2 h. The product is cooled under a stream of H2Se-h He and subsequently outgassed at ca. 1075 Kat 10" Torrto remove adsorbed H2Se and Se. The dark khaki colored EuSe sample appeared insensitive to the laboratory atmosphere, Hariharan, Eick [12]. EuSe from the reaction of EUSO4 with H2Se is often contaminated by EuS, Pink [13]. The compound is obtained by reduction of europium oxalate at 800 to 900°C ... 

Scanning electron microscopy shows the cement to consist of zinc oxide particles embedded in an amorphous matrix (Smith, 1982a). As with the zinc phosphate cement, a separate globular water phase exists since the cement becomes uniformly porous on dehydration. Porosity diminishes as the water content is decreased. Wilson, Paddon Crisp (1979) distinguish between two types of water in dental cements non-evaporable (tightly bound) and evaporable (loosely bound). They found, in the example they examined, that the ratio of tightly bound to loosely bound water was 0-22 1-0, the lowest for all dental cements. They considered that loosely bound water acted as a plasticizer and weakened the cement. 

Fito, P., Chiralt, A., Betoret, N., Gras, M., Chafer, M., Martinez-Monzo, J., Andres, A., and Vidal, D. 2001b. Vacuum impregnation and osmotic dehydration in matrix engineering Application in functional fresh food development. J. Food Engineer. 49, 175-183. 

Liquid-solid separations, pilot plant, 18 731 Liquid-solid suspension, effective thermal conductivity of, 13 277 Liquid-state metal-matrix composite processing, 16 166-169 Liquid steel, 23 250 Liquid stream dehydration, molecular sieves in, 16 840... 

Further evidence for microphase separahon has been seen by AFM. As expected, BPSH 00, with no ionic regions, displays no significant features in its AFM image. For BPSH 20, isolated ionic clusters have dimensions of 10-25 nm. These clusters are even more readily discerned from the non-ionic matrix in BPSH 40, but the domains appear to remain relatively segregated from each other. In the case of BPSH 50 and 60, connections between domains are clearly visible, especially in the case of the latter sample. It also should be noted, however, that these samples were in a dehydrated state. Therefore, it might be expected that even in the case of the lower acid content samples, it is likely that some channel formation between ionic domains will still occur upon the uptake of water. This can be clearly seen in its linear conductivity behavior as a function of disulfonated monomer (i.e., the percolation threshold has been reached by at least 20-30% content of disulfonated monomer). 

The aqueous fluids formed by melting of ices in asteroids reacted with minerals to produce a host of secondary phases. Laboratory studies provide information on the identities of these phases. They include hydrated minerals such as serpentines and clays, as well as a variety of carbonates, sulfates, oxides, sulfides, halides, and oxy-hydroxides, some of which are pictured in Figure 12.15. The alteration minerals in carbonaceous chondrites have been discussed extensively in the literature (Zolensky and McSween, 1988 Buseck and Hua, 1993 Brearley, 2004) and were most recently reviewed by Brearley (2006). In the case of Cl chondrites, the alteration is pervasive and almost no unaltered minerals remain. CM chondrites contain mixtures of heavily altered and partially altered materials. In CR2 and CV3oxb chondrites, matrix minerals have been moderately altered and chondrules show some effects of aqueous alteration. For other chondrite groups such as CO and LL3.0-3.1, the alteration is subtle and secondary minerals are uncommon. In some CV chondrites, a later thermal metamorphic overprint has dehydrated serpentine to form olivine. 

The CV, CO, and CR chondrites are mostly anhydrous and were considered in Chapter 11. However, the CV3oxB chondrites experienced significant aqueous alteration. The matrices of these meteorites are heavily altered and contain phyllosilicates, fayalite, Fe,Ni sulfides and carbides, Ca,Fe pyroxene, and andradite garnet. The CVoxA chondrites were apparently also aqueously altered, but were subsequently dehydrated by thermal metamorphism. The matrices of CR2 chondrites contain alteration minerals that resemble those in Cl chondrites, including phyllosilicates, magnetite (Fig. 12.15d), carbonates and sulfides, although the alteration is not as extensive. Chondrule mesostasis was affected in some CR chondrites. Minor phyllosilicates occur in the matrix of chondrites, but these meteorites contain no carbonates or sulfates. 

The same behavior has already been observed with whole dehydrated cells of Saccharomyces cerevisiae [11] or immobilized ADH in the gas phase [45]. It seems also that the cellular matrix increases the need for hydration to perform catalysis. 

Drzal et al. 90) have investigated the effect of interphase modification on interfacial moisture absorption. The fibers used were a surface treated and a surface treated and finished type A carbon fiber in the same epoxy matrix studied previously. Three equilibrium exposure conditions were investigated. 20 °C, 70 °C and 120 °C were selected for moisture equilibration of single fiber samples and for the neat epoxy resin. The interfacial shear strength was measured both in the saturated and the dehydrated cases and compared to the initial dry values. 

Figure 22 is a plot of the initial tensile modulus of the epoxy matrix after equilibrium moisture exposure and dehydration. At both 20 °C and 70 °C, the effect of moisture absorption on the matrix is reversible as evidenced by the reattainment of dry properties. The exposure at 125 °C is not completely reversible as shown by the data. 

Exposure at 125 °C is very severe for this epoxy matrix (Fig. 25). Permanent changes in the matrix are noted. The interphase layer, however, acts to mitigate some of the deleterious interfacial effects and allows that system to regain a larger portion of its interfacial shear strength after moisture exposure and dehydration. The fiber without the finish layer has lost almost all of its interfacial shear strength and recovers very little after dehydration. 

For extraction of nonpolar analytes, drying agents are mixed with the matrix to adsorb moisture before extraction. Hydromatrix (Celite 566) has been used frequently. Sodium sulfate, and calcium sulfate (Drierite) are also used to dehydrate the matrix. Ratios of sample to drying agent of 1 1 up to 1 5 have been... 

Extraction of sulfonamides and diaminopyrimidine potentiators from edible animal products should render the bound residues soluble, remove most or all of the proteins, and provide high yields for all analytes. Sample extraction/deprotei-nization is traditionally accomplished with polar solvents including acidic aqueous solutions (211,214-222), acetonitrile (56,223-232), chloroform (233-240), ethyl acetate (29,241-244), dichloromethane (204,242,245-247), acetone (194, 248, 249), or various combinations of them. Use of dichloromethane at pH 10 in the presence of an ion-pairing reagent (tetrabutylammonium) has also been reported to work extremely well in the extraction of sulfadimethoxine and ormeto-prim residues from catfish muscle (250) and animal tissues (251). Anhydrous sodium sulfate may be added to dehydrate tissue samples to permit better exposure of the matrix to tire solvent. 

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