Dispersive solvent

The term "hydrophobic interaction" unfortunately implies some form of molecular repulsion, which, outside the van der Waals radii of a molecule, is quite impossible. The term "hydrophobic force" literally means "fear of water" force. The term hydrophobic has been introduced as an alternative to dispersive but means the same. It is not clear from the literature how the word hydrophobic originated, but it may have been provoked by the immiscibility of a dispersive solvent such as n-heptane with a very polar solvent such as water. 

Consider the bi-layer adsorption of strongly polar solvent (B) (e.g., ethyl acetate) from a solution in a dispersive solvent (A) (e.g., n-heptane) onto a silica gel surface, as depicted in Figure 6. 

From the point of view of solute interaction with the structure of the surface, it is now very complex indeed. In contrast to the less polar or dispersive solvents, the character of the interactive surface will be modified dramatically as the concentration of the polar solvent ranges from 0 to l%w/v. However, above l%w/v, the surface will be modified more subtly, allowing a more controlled adjustment of the interactive nature of the surface It would appear that multi-layer adsorption would also be feasible. For example, the second layer of ethyl acetate might have an absorbed layer of the dispersive solvent n-heptane on it. However, any subsequent solvent layers that may be generated will be situated further and further from the silica surface and are likely to be very weakly held and sparse in nature. Under such circumstances their presence, if in fact real, may have little impact on solute retention. 

The more dispersive solvent from an aqueous solvent mixture is adsorbed onto the surface of a reverse phase according to Langmuir equation and an example of the adsorption isotherms of the lower series of aliphatic alcohols onto the surface of a reverse phase (9) is shown in figure 9. It is seen that the alcohol with the longest chain, and thus the most dispersive in character, is avidly adsorbed onto the highly dispersive stationary phase, much like the polar ethyl acetate is adsorbed onto the highly polar surface of silica gel. It is also seen that... 

In contrast, the mono-layer of methanol is built up much more slowly and is not complete until the concentration of methanol in the aqueous mixture is about 35%w/v. The behavior of methanol on the reverse phase is reminiscent of the adsorption of chloroform on the strongly polar silica gel surface. The complementary nature of the silica gel surface and that of the reverse phase is clearly apparent. It is also clear that strongly dispersive solvents might form bi-layers on the reverse phase surface just as polar solutes form bi-layers on the highly polar surface of silica gel. In fact, to date there has been no experimental evidence furnished that would support the formation of bi-layers on the surface of reverse phases, although their formation is likely and such evidence may well be forthcoming in the future. 

Increasing the solvent concentration increases the level of the competitive dispersive interactions that take place in the mobile phase. Use of a more dispersive solvent, such as tetrahydrofuran, will also achieve the same effect. In the same way, use of a more polar solvent such as methanol will increase the competitive polar interactions in the mobile phase. 

M. Ash and I. Ash, Dispersants, Solvents and Solubilizers, Edward Arnold Publishers, London (1988). 

A-EtFOSE, A-EtFOSAA, FOSAA, FOSA, N-EtFOSA, PFOSI (perfluorooctane sulfinate), PFOA, PFOS Solid-liquid extraction — Sonication and centrifugation — Extract poured into a new tube + MeOH — Purification by dispersed solvent (ENVI-Carb) — (in parallel) SPE from headspace sampling LC-ESI-MS-MS (QqQ) 0.1 pg/L (vial)a 46-49 pmol (microcosm)3 [85]... 

One may wonder why lobsters appear to use urine as a dispersal solvent for chemical signals, whereas terrestrial arthropods such as the well-studied insects use direct release of gland products into the air. Perhaps the answer is that small animals in air (such as insects) are always in danger of desiccation. By contrast, marine lobsters and crabs are relatively large and may experience only minor water loss problems due to osmosis. Thus, it may not be difficult for a 500-g lobster to store 10 ml of urine and release it during a dominance battle at a rate of up to 1 ml/min (27). The advantage of urine-carried pheromones is that the dispersal mechanism already exists urine is injected into the gill current, which in turn injects into ocean currents. 

It can be clearly seen from equation (9) that the expression for the retention volume of a solute, although generally correct, is grossly over simplified if accurate measurements of retention volumes are required Some of the stationary phase may not be chromatographically available and not all the pore contents have the same composition as the mobile phase and, therefore, being static, can act as a second stationary phase. This situation is akin to the original reverse phase system of Martin and Synge where a dispersive solvent was absorbed Into the pores of support to provide a liquid/liquid system. As a consequence a more accurate form of the retention equation would be,... 

Patil, C.B. Mohapatra, P.K. Singh, R.R. Gurba, P.B. Janardan, P. Changrani, R.D. Manchanda, V.K. Transport of uranium from nitric acid solution by non-dispersive solvent extraction using a hollow fibre contactor, Radiochim. Acta 94 (2006) 331-334. 

Christopher J. Cramer and their co-workers during the last decade [61,100, 55, 56], In SMx, terms responsible for cavity foimation. dispersion, solvent structure and local field polarization are present [51,57], The solvation energy is obtained via the usual approximation that the solute, treated at the quantum mechanical level, is immersed in an isotropic polarizable continuum representing the solvent. Therefore the standard free energy of the solute in solution can be expressed as ... 

Step 5. Calculate the dispersed solvent-phase velocity next, using Eq. (7.23) ... 

Fouad, E.A. and Bart, H.J. (2007) Separation of zinc by a non-dispersion solvent extraction process in a hollow-fiber contactor. Solvent Extraction and Ion Exchange, 25, 857. 

Alonso,A.I., Urtiaga,A.M., Zamacona, S., Irabien, A. and Ortiz, I. (1997) Kinetic modelling of cadmium removal from phosphoric acid by non-dispersive solvent extraction. Journal of Membrane Science, 130, 193. 

Galan, B., Castaneda, D. and Ortiz, I. (2008) Integration of ion exchange and non-dispersive solvent extraction processes for the separation and concentration of Cr(VI) from ground waters. Journal of Hazardous Materials, 152, 795. 

Kumar, A., Haddad, R., Alguacil, F.J. and Sastre, A.M. (2005) Comparative performance of non-dispersive solvent extraction using a single module and the integrated membrane process with two hollow-fiber contactors. Journal of Membrane Science, 248, 1. 

Oleoresin Pimenta Berries Obtained by the solvent extraction of the dried fruit of Pimenta officinalis Lindl (Fam Myrtaceae) as a brown-green to dark green liquid. Oleoresin Rosemary Obtained by the solvent extraction of the dried leaves of Rosmarinus officinalis L. (Fam. Labiatae). It is a thick, green paste that can be diluted with food-grade water- or oil-dispersible solvents. It may have a reduced chlorophyll content. The volatile oil content varies depending on its intended effect from a highly camphoraceous note to a subtle herbal note. 

Micelle preparation starts from the design of the block copolymer precursors. Even if two blocks of the copolymer have to be incompatible in order to guide the self-assembly, their solubility in the dispersion solvent can vary between two extreme cases (1) the two blocks can have a different solubility such that the use of a selective solvent will trigger the micelle formation and (2) the two blocks can have the same solubility, the solvent being non-selective. In this case, micelles will be produced by the in situ formation of multiple cross-linking points. 

Solubility The amount of mass of a substance or chemical that will dissolve in a unit volume of solution aqueous solubility is the maximum concentration of a chemical that will dissolve in pure water at a reference temperature Solution A mixture in which the components are uniformly dispersed Solvent A liquid capable of dissolving or dispersing one or more chemical substances in certain instances the solvents can dissolve many different chemical substances—for instance, water, ethanol, acetone, hexane, and toluene Soot An agglomeration of particles of carbon impregnated with tar formed in the incomplete combustion of carbonaceous material Sorbent A solid or liquid medium in or upon which materials are retained by absorption or adsorption... 

Based on the modes of lipid dispersion, the methods of liposomes formation can be classified into three categories mechanical dispersion, solvent dispersion, and detergent solubilization (175). These generally involve the following stages as evident in Figure 8.23. 

FIGURE 33.11 Effect of U(VI) concentration on extraction using non-dispersive solvent extraction (NDSX) technique. (From Gupta, S.K. et al., J. Membr. Sci. 300, 131, 2007. With permission.)... 

Basu R., Prasad P., and Sirkar, K., Non-dispersive solvent back-extraction of phenol. AIChE J. 36, 450-460, 1990. 

Alonso A., Galan B., Gonzalez M., and Ortiz M.I., Experimental and theoretical analysis of a non-dispersive solvent extraction pilot plant for the removal of Cr(VI) from a galvanic process wastewater. Irui. Eng. Chem. Res. 38, 1666, 1999. 

Galan B., San Roman F., Irabien A., and Ortiz L, Viability of the separation of Cd from highly concentrated Ni-Cd mixtures by non-dispersive solvent extraction. Chem. Eng. J. 70, 237, 1998. 

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