Solvents, adsorption

Problems with adsorption onto the packing material are more common in aqueous GPC than in organic solvents. Adsorption onto the stationary phase can occur even for materials that are well soluble in water if there are specific interactions between the analyte and the surface. A common example of such an interaction is the analysis of pEG on a silica-based column. Because of residual silanols on the silica surface, hydrogen bonding can occur and pEG cannot be chromatographed reliably on silica-based columns. Eikewise, difficulties are often encountered with polystyrenesulfonate on methacrylate-based columns. 

Trasatti, S. Solvent Adsorption and Double-Layer Potential Drop at Electrodes 13... 

Solvent adsorption. The adsorption of solvent molecules is manifested in their orientation and ordered arrangement at the interface. 

When an electrode comes in contact with an elecholyte solution, then apart from a possible adsorption of different solution components, another phenomenon occurs (i.e., a certain orientation of all dipolar solvent molecules that are close to the surface, with respect to this surface). Sometimes this is discussed as solvent adsorption including the formation of a monolayer of solvent molecules at the surface. 

In case of solvent recovery some units feature a water separator permitting recycling of the recovered solvent. Adsorption processes are discussed in Chapter 17. 

In a recent paper (70 Hartman studies the effect of surface relaxation on the habit of corundum and hematite. The habits observed on natural and synthetic crystals of these systems did not agree with calculated relaxed equilibrium or growth habits. Hartman concluded that these observations could be understood by invoking specific solvent adsorption on (111) faces. 

In flow microcalorimetry a small sample is put into the cell of the calorimeter and the probe molecule passes through it in an appropriate solvent. Adsorption of the probe results in an increase in temperature and integration of the area under the signal gives the heat of adsorption [70]. This quantity can be used for the calculation of the reversible work of adhesion according to Eq. 13. The capabilities of the technique can be further increased if a HPLC detector is attached to... 

As will be shown, the equation rates obtained for o-HAP formation in the case of strong (polar sulfolane) and weak (nonpolar dodecane) solvent adsorption (Figure 2.3) explain the inhibiting effect of sulfolane as well as the differences in reaction order with respect to PA in the polar (order 1) and nonpolar (order 0.5)... 

Fractal geometry was employed to study surface geometry effects on adsorption conformations of polymers.1771 Using poly(styrene) for the case study, it was shown, that for highly porous objects, solution conformation changed very little after solvent adsorption. 

Here II = yo - y is the surface pressure, k the Boltzmann constant, and (Oo the solvent molecule molecular area. An important feature of Eq. (6) is that it involves solvent characteristics only. The (Oo value depends on the choice of the position of the dividing surface. Assuming the solvent adsorption to be positive, the equation was proposed30 which relates the surface excesses H of the solvent (subscript i = 0) and dissolved species (i > 1) with any molecular area (fy ... 

Study of the V-typc sample (Table 2) has shown that D, D2, and D3 doses inhibit cell growth by 9.7, 18.6, and 24.2%, respectively. This is close to the effect of Platidiam Ptd-L solution from which the drug adsorption was carried out. Results obtained show that almost all Platidiam is released from the magnetically sensitive carrier into the cultivated medium. Increased cytostatic action of magnetically sensitive nanocomposites (Platidiam carriers) may be achieved by means of solvent, adsorption time, and temperature optimization. 

Fig. 27.8. C02 recovery by solvent adsorption process. (Courtesy Process Systems Consulting, Inc.)...

Utilized selective anisotropic solvent adsorption on specific crystal faces to favour the growth of morphologically polar crystals. Some additional reports of the study of crystal modification and nonlinear optical activity include those on anhydrous and hydrated sodium / -nitrophenolate (Brahadeeswaran et al. 1999), derivatives of 2-benzylideneindan-l,3-dione (Matsushima et al. 1992), straight-chain carbamyl compounds (Francis and Tiers 1992), benzophenone derivatives (Terao et al. 1990), a 1,3-dithiole derivative (Nakatsu et al. 1990), o -[(4 -methoxyphenyl)methylene]-4-nitro-benzene-acetonitrile (Oliver et al. 1990) and so-called lambda shaped molecules (Yamamoto et al. 1992). Hall et al. (1988) followed the thermal conversion of the centrosymmetric P2 /c) form of 2,3-dichloroquinazirin to the non-centrosymmetric Pc form by monitoring the development of an SHG signal. Consistent with the earlier observation, the centrosymmetric form was obtained under equilibrium conditions, while the non-centrosymmetric one could be obtained under more kinetic conditions. 

S. Trasatti, Solvent adsorption and double-layer potential drop at electrodes, in Modem Aspects of Electrochemistry. Vol. 13, B. E. Conway and J. O M. Bockris, editors. Plenum Press, New York, 1979,... 

S. Trasatti. The Electrode Potential, in Comprehensive Treatise of Electrochemistry, Vol. 1, J. O M. Bockris, B.E. Conway and E. Veager. Eds. Plenum (1980), chapter 2 B.E. Conway, The State of Water and Hydrated Ions at Interfaces, Adv. Colloid Interface Sci. 8 (1977) 91 W.R. Fawcett, Molecular Models for Solvent Structure at Polarizable Interfaces. Isr. J. Chem. 18 (1979) 3 M.A. Habib, Solvent Dipoles at the Electrode-Solution Interface. in Modem Aspects of Electrochemistry, Vol. 12, J. O M. Bockris and B.E. Conway. Eds. Plenum (1977) 131 S. Trasatti, Solvent Adsorption and Double Layer Potential Drop at Electrodes, in Modem Aspects of Electrochemistry, B.E. Conway and J. O M. Bockris, Eds. Vol. 13 Plenum (1979) chapter 2 J. O M. Bockris. K-T. Jeng, Water Structure at Interfaces The Present Situation. Adv. Colloid Interface Set 33 (1990) 1. 

Sorption of VOCs involves the processes of adsorption and partitioning. Partitioning is the incorporation of the VOC into the natural organic matter associated with the solid and is analogous to the dissolution of an organic compound into an organic solvent. Adsorption is the formation of a chemical or physical bond between the VOC and the mineral surface of a solid particle (Rathbun, 1998). The equilibrium relation between aqueous and solid phase concentrations then is expressed as... 

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