Phase oleic

By comparing the relative rate of uptake of two different lipid probe molecules, another piece of evidence for a monomeric mechanism in lipid uptake by membranes has been found. Hoffman [70] and Hoffman and Yeoh [71] have determined the relationship between micellar concentration and uptake by rat small intestine in vitro for oleic acid and a monoglyceride analog, a 1-monoether. They found that the rate of uptake for both of the two micellar solutes was linearly dependent on the micellar concentration, but that the ratio of rate of uptake was different from the molar ratio of the two lipids in the micellar phase. Oleic acid was absorbed more rapidly than the monoether, probably due to a higher monomer concentration in the... 

Numerous bioreduction examples use an organic solvent to form a second phase from extractive ISPR. For example, extractive ISPR in a two-phase system was used to remove 2-phenylethanol, giving an increase of one order of magnitude in product concentration and also productivity [41]. The two-phase system was ultimately limited by mass transfer on account of high viscosity of the chosen organic phase (oleic acid). In common with many such processes, it is clear that far more work is required on solvent selection. Interestingly the dissolved level of solvent in water is always exposed to the biocatalyst (whether the ISPR is internal or external) and in many cases this causes a detrimental effect to the biocatalyst over time. 

Phase Behaviour In more general models there can be three or even more phases with mass transfer between phases. For example the black oil model is a three component system of oil, gas and water components separating into three phases oleic, gaseous and aqueous. Gas can move between the oleic, gaseous and aqueous phases. The oleic phase is a mixture of oil and gas, the aqueous phase a mixture of water and gas, and the gaseous phase is just gas. 

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. 

In Figure 1, the pairs (or triad) of phases that form ia the various multiphase regions of the diagram are illustrated by the corresponding test-tube samples. Except ia rare cases, the densities of oleic phases are less than the densities of conjugate microemulsions and the densities of microemulsions are less than the densities of conjugate aqueous phases. Thus, for samples whose compositions He within the oleic phase-microemulsion biaodal, the upper phase (ie, layer) is an oleic phase and the lower layer is a microemulsion. For compositions within the aqueous phase-microemulsion biaodal, the upper layer is a microemulsion and the lower layer is an aqueous phase. When a sample forms two layers, but the amphiphile concentration is too low for formation of a middle phase, neither layer is a microemulsion. Instead the upper layer is an oleic phase ("oil") and the lower layer is an aqueous phase ("water"). 

In three-phase systems the top phase, T, is an oleic phase, the middle phase, Af, is a microemulsion, and the bottom phase, B, is an aqueous phase. Microemulsions that occur ia equiUbrium with oae or two other phases are sometimes called "limiting microemulsions," because they occur at the limits of the siagle-phase regioa. 

The locations of the tietriangle and biaodal curves ia the phase diagram depead oa the molecular stmctures of the amphiphile and oil, on the concentration of cosurfactant and/or electrolyte if either of these components is added, and on the temperature (and, especially for compressible oils such as propane or carbon dioxide, on the pressure (29,30)). Unfortunately for the laboratory worker, only by measuriag (or correcdy estimatiag) the compositions of T, Af, and B can one be certain whether a certain pair of Hquid layers are a microemulsion and conjugate aqueous phase, a microemulsion and oleic phase, or simply a pair of aqueous and oleic phases. 

However, often the identities (aqueous, oleic, or microemulsion) of the layers can be deduced rehably by systematic changes of composition or temperature. Thus, without knowing the actual compositions for some amphiphile and oil of poiats T, Af, and B ia Figure 1, an experimentaUst might prepare a series of samples of constant amphiphile concentration and different oil—water ratios, then find that these samples formed the series (a) 1 phase, (b) 2 phases, (c) 3 phases, (d) 2 phases, (e) 1 phase as the oil—water ratio iacreased. As illustrated by Figure 1, it is likely that this sequence of samples constituted (a) a "water-continuous" microemulsion (of normal micelles with solubilized oil), (b) an upper-phase microemulsion ia equiUbrium with an excess aqueous phase, ( ) a middle-phase microemulsion with conjugate top and bottom phases, (d) a lower-phase microemulsion ia equiUbrium with excess oleic phase, and (e) an oA-continuous microemulsion (perhaps containing iaverted micelles with water cores). 

Nevertheless, possibiUties for confusion abound. From the definitions of microemulsions and macroemulsions and from Figure 1, it immediately follows that in many macroemulsions one of the two or three phases is a microemulsion. Until recentiy (49), it was thought that all nonmultiple emulsions were either oil-in-water (O/W) or water-in-oil (W/O). However, the phase diagram of Figure 1 makes clear that there are six nonmultiple, two-phase morphologies, of which four contain a microemulsion phase. These six two-phase morphologies are oleic-in-aqueous (OL/AQ, or O/W) and aqueous-in-oleic (AQ/OL, or W/O), but also, oleic-in-microemulsion (OL/MI), microemulsion-in-oleic (MI/OL), aqueous-in-microemulsion (AQ/MI), and microemulsion-in-aqueous (MI/AQ) (49). 

Fig. 8. Emulsion morphology diagram, illustrating where the microemulsion in various macroemulsion morphologies is a continuous phase or dispersed phase. Morphology boundaries (—), aqueous, continuous (--------------), oleic, continuous (--), microemulsion, continuous.

The most commonly used emulsifiers are sodium, potassium, or ammonium salts of oleic acid, stearic acid, or rosin acids, or disproportionate rosin acids, either singly or in mixture. An aLkylsulfate or aLkylarenesulfonate can also be used or be present as a stabilizer. A useful stabilizer of this class is the condensation product of formaldehyde with the sodium salt of P-naphthalenesulfonic acid. AH these primary emulsifiers and stabilizers are anionic and on adsorption they confer a negative charge to the polymer particles. Latices stabilized with cationic or nonionic surfactants have been developed for special apphcations. Despite the high concentration of emulsifiers in most synthetic latices, only a small proportion is present in the aqueous phase nearly all of it is adsorbed on the polymer particles. 

Preparation of Emulsions. An emulsion is a system ia which one Hquid is coUoidaHy dispersed ia another (see Emulsions). The general method for preparing an oil-ia-water emulsion is to combine the oil with a compatible fatty acid, such as an oleic, stearic, or rosia acid, and separately mix a proportionate quantity of an alkah, such as potassium hydroxide, with the water. The alkah solution should then be rapidly stirred to develop as much shear as possible while the oil phase is added. Use of a homogenizer to force the resulting emulsion through a fine orifice under pressure further reduces its oil particle size. Liquid oleic acid is a convenient fatty acid to use ia emulsions, as it is readily miscible with most oils. 

FIG. 10 (a)n-A isotherms for oleic acid-capped silver particles the labels refer to the different phases as described in the text, (b) BAM micrographs at surface areas of (a) 5000-nm particle (b) 3200-nm particle during compression, (c) 1500-nm particle during compression, and (d) 5000-nm particle after re-expansion. The scale bar represents 1 mm. The micrographs are identified by the letters in the upper left corner of each image. (Reprinted with permission from Ref. 111. Copyright 1996 American Chemical Society.)... 

Scheme 4.3 Two-phase lipase catalysed esterification of oleic acid.

Figure 4.4 Continuous two-phase hpase catalysed esterification of oleic acid in the CCS (a) Both phases once through, (b) Aqueous phase full recycle organic phase 90% recycle.

The estimation of flow functions from an actual experiment is reported next. A multi-rate primary drainage experiment was conducted on a Texas Cream limestone sample. Hexadecane was used as the oleic phase and deuterium oxide (D20) was used as the aqueous phase. Protons are imaged, so only the oil phase is observed. The pressure drop data, production data and saturation data are shown in Figures 4.1.11-... 

Table I shows the composition of lipo-PGEj. Oleic acid was used to improve the stability of PGEj. Glycerol was added to make the water phase isotonic. Isocarbacyclin, a prostacyclin derivative (TEI9090), was incorporated into the lipid microspheres (lipo-PGI2) in a similar composition except for the use of oleic acid.

Inverse emulsification A solution of the polymer within a volatile, water-immiscible organic solvent (or mixture of solvents) or a polymer melt is compounded with a long-chain fatty acid (e.g., oleic acid) using conventional rubbermixing equipment and mixed slowly with a dilute aqueous phase to give a W/O emulsion,... 

Isaacs and Smolek [211 observed that low tensions obtained for an Athabasca bitumen/brine-suIfonate surfactant system were likely associated with the formation of a surfactant-rich film lying between the oil and water, which can be hindered by an increase in temperature. Babu et al. [221 obtained little effect of temperature on interfacial tensions however, values of about 0.02 mN/m were obtained for a light crude (39°API), and were about an order of magnitude lower than those observed for a heavy crude (14°API) with the same aqueous surfactant formulations. For pure hydrocarbon phases and ambient conditions, it is well established that the interfacial tension behavior is dependent on the oleic phase [15.231 In general, interfacial tension values of crude oiI-containing systems are considerably higher than the equivalent values observed with pure hydrocarbons. 

Chlorination of oleic acid dissolved in carbon tetrachloride was tested in a flow reactor. The data are at 12.8 C (Roper, Chem Eng Sci 227, 1953). The reactants were dissolved separately and mixed in the liquid phase at the inlet to the reactor. Show that the reaction is second order. 

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