Preparation of the Emulsions

The aim of this study was to investigate the differences in stability between water-in-crude oil emulsions with and without the addition of solid particles. Both crude A and crude B emulsions were used for the testing procedures. The effect of increasing the amount of crude A asphaltenes to the same as in crude B (from 0.76 to 1.65%) was also examined. 

Simple water-in-crude oil emulsions were prepared by mixing the same volume of crude oil and synthetic sea water (3.5 wt% Nad) at 40 °C. Oil and water were poured into a glass tube (total amount 25 mL). Each emulsification was performed with an Ultra Turrax (IKA, T18 with 10 and 6.75 mm of stator and rotor diameters, respectively) at 21500 rpm and 40 °C for 3 min, just before proceeding with droplet size determination and stability measurements. 

To prepare modified emulsions, first asphaltenes and then solid particles were added to the oil phase, before emulsifying with water When no addition of asphaltenes was required, particles were dispersed in the crude oil. Subsequently, the glass tube was placed on a shaking table for 5 h at 300 min and then in a oven at 40 ° C for 3 6 h to allow the adsorption of crude oil components to proceed. In the case where the total amount of asphaltenes of crude A was increased to 1.65%, asphaltenes extracted from cmde A were added to the oil phase before dispersing the particles. The sample was then placed on a shaking table at 300 min for 5 h, then for 36h in an oven at 60 °C and, finally, cooled to 40 ° C before particle addition and subsequent mixing with water. 

Addition of crude A asphaltenes and particles was also performed on model oil emulsions of 50% water cut The model oil phase consisted of a 70 30 v/v exxolDSO toluene mixture. All procedures were carried out as previously specified. All samples were analyzed by microscopy and the asphaltenes found solubflized. 

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Bailey, A.L, Cardenas-Valera, A.E., Graft copolymers as stabilizers for oil-imwater emulsions. Part 2. Preparation of the emulsions and the factors affecting their stability. Colloids and Surfaces, v.97, pp.1-12, 1995. 

Since a-tocopherol destroys nitrite in the system in absence of the oil phase, we may postulate that the ineffectiveness of these two oil soluble inhibitors resulted from their absence from the aqueous phase. Diethanolamine is miscible with water and presumably its nitrosation occurs in the aqueous phase. There is a significant difference in the solubility characteristics of ascorbyl palmitate. The reducing portion of the molecule is water soluble. Thus the ascorbate moiety may be in the aqueous phase while the fatty acid tails may lie within the oil globules. The a-tocopherol and the BHA may well be effective if they are dispersed in the aqueous phase after preparation of the emulsion. This will be investigated in future experiments. 

Some chemical sensitization may occur even in emulsions prepared with the treated gelatin because of incomplete removal of chemical sensitizers by the treatment used. For this reason it is more precise to refer to these emulsions as "without deliberate chemical sensitization" rather than as "unsensitized," but the latter term is less cumbersome and is used rather commonly in the literature. I shall use it in this chapter with the understanding that it means simply that a deliberate chemical sensitization step was not included in the preparation of the emulsion. 

Per mouse a volume of 100 pi is injected. Before preparation of the emulsion, calculate the total volume of emulsion needed and multiply that by 2 to provide excess for practical losses. A significant portion of the emulsion will be lost due to dead needle volume and refilling of the syringe. For example, when 40 mice need to be injected,... 

The size distribution curve of the droplets in the emulsions varied little if soaps of sodium, potassium, or caesium were used. As a rule the curves had a marked peak, at a diameter of about 2fi, which apparently depended little on the manner of preparation of the emulsion, and slightly on the nature of the oil. Emulsions of water in oil, stabilized by magnesium or aluminium soaps, had a similar distribution of sizes among the droplets. 

Collodion can be substituted for gelatin in the preparation of the emulsion, but the plates are less sensitive than the gelatin plates. Gelatin exerts a reducing action on silver bromide, but collodion does not the collodion plates are consequently free from the trace of fog characteristic of gelatin plates, and therefore give a very sharp, well-defined image suitable for technical reproduction. Collodion plates are rendered more sensitive by the presence of silver nitrate in the emulsion but such plates have to be exposed in the wet condition, and are not well adapted for field work. The increase in sensitiveness depends on the reaction... 

With cetyl alcohol, there is the complication that the polarity of the molecule may cause it to reside at the surface of the droplet, imparting additional colloidal stability. Here, the surfactant and costabilizer form an ordered structure at the monomer-water interface, which acts as a barrier to coalescence and mass transfer. Support for this theory lies in the method of preparation of the emulsion as well as experimental interfacial tension measurements [79]. It is well known that preparation of a stable emulsion with fatty alcohol costabilizers requires pre-emulsification of the surfactants within the aqueous phase prior to monomer addition. By mixing the fatty alcohol costabilizer in the water prior to monomer addition, it is believed that an ordered structure forms from the two surfactants. Upon addition of the monomer (oil) phase, the monomer diffuses through the aqueous phase to swell these ordered structures. For long chain alkanes that are strictly oil-soluble, homogenization of the oil phase is required to produce a stable emulsion. Although both costabilizers produce re-... 

Ultrasound-assisted emulsification in aqueous samples is the basis for the so-called liquid membrane process (LMP). This has been used mostly for the concentration and separation of metallic elements or other species such as weak acids and bases, hydrocarbons, gas mixtures and biologically important compounds such as amino acids [61-64]. LMP has aroused much interest as an alternative to conventional LLE. An LMP involves the previous preparation of the emulsion and its addition to the aqueous liquid sample. In this way, the continuous phase acts as a membrane between both the aqueous phases viz. those constituting the droplets and the sample). The separation principle is the diffusion of the target analytes from the sample to the droplets of the dispersed phase through the continuous phase. In comparison to conventional LLE, the emulsion-based method always affords easier, faster extraction and separation of the extract — which is sometimes mandatory in order to remove interferences from the organic solvents prior to detection. The formation and destruction of o/w or w/o emulsions by sonication have proved an effective method for extracting target species. 

The viscoelastic parameters reached maximum values within one hour after preparation of the emulsions and then they decreased continuously as the emulsions were aged. The Eq values (Pa) of freshly prepared mayoimaise increased as the pH decreased pH 6.2, o = 750 pH 4.5, Eq = 885 pH 3.9, Eq = 1220 and pH 3.3, Eq = 1351. There was a substantial decrease in the viscoelasticity parameters as the emulsions were aged at room temperature at all values of pH except at pH 6.2. 

The first step is the preparation of the emulsion containing the adjuvant and the antigen. For each mouse, 500 pg of mBSA must be dissolved in a final volume of 100 pL (50 pL of CFA+ 50 pL of PBS). There are significant losses during the preparation and injection and this must be taken into consideration when deciding the amount of material to be prepared. 

To prepare any of the above systems, the formulation chemist must choose an optimum emulsifier system that is suitable for the preparation of the emulsion and maintenance of its long-term physical stability. The oil that may be used as drug carrier has to be nontoxic, e.g. vegetable oils (soybean and safflower), synthetic glycerides (including simulated human fats), and acetoglycerides. 

Nanoprecipitation uses preformed polymers to prepare PNPs. Hence, preparation of the emulsion before the initiation of the process is not necessary in nanoprecipitation. Precipitation of polymer occurs under spontaneous dispersion of the polymer solution. Use of preformed polymers rather than monomers provides simplicity to the process and minimizes the probability of introducing foreign particles in the nanopaiticles. Nanoprecipitation is considered as the simple, reproducible, economical, less toxic, and efficient process in encapsulation [12-14]. 

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