Tetradecane emulsions

Figure 23. The lateral diffusion coefficient of adsorbed FITC-/8-lg in thin films as a function of added Tween 20. (a), o/w thin films formed from aqueous non-homogenized solutions of /3-lg at 3 mg/ml ( ), o/w thin films formed from 10% v/v n-tetradecane emulsion or emulsion subnatant samples of FITC-/3-lg, initial protein concentration 3 mg/ml ( ), a/w thin films formed from aqueous non-homogenized solutions of /3-lg at 0.2 mg/ml.

G. Narsimham and P. Goel Drop Coalescence During Emulsion Eormation in a High-Pressure Homogenizer for Tetradecane-in-Water Emulsion Stahihzed hy Sodium Dodecyl Sulfate. J. Colloid Interface Sci. 238, 420 (2001). 

Displacement of the protein from the adsorbed layer in o/w thin films shows very different behavior from its a/w counterpart. Although displacement of protein from the o/w interfaces initiates at approximately the same solution composition (i.e., R = 0.1), there is little evidence for the stepwise displacement observed in the a/w thin films. This observation is further confirmation of the monolayer versus multilayer structure at the o/w and a/w thin films. The displacement of /3-lg has also been investigated in oil-in-water emulsions of n-tetradecane [46,47], In these reports it was shown that the protein was not completely displaced until R = 10, which was considerably higher than R = 1 - 2 in Figure 22. This will be discussed further below. 

Figure 3.24 Left emulsion type depending on the temperature and surfactant concentration (C- 2E5) for a constant tetradecane/water ratio of 1 1. Right interfacial tension as a function of the temperature of the system tetradecane/water/C Es.

We have developed new reaction systems based on colloidal dispersions [23, 24], namely highly concentrated water-in-oil (gel) emulsions, which could overcome most of the disadvantages of the aqueoussolvent mixtures such as inactivation of the aldolase and incomplete aldehyde solubilization in the medium. These emulsions are characterized by volume fractions of dispersed phase higher than 0.73 [25] therefore, the droplets are deformed and/or polydisperse, separated by a thin film of continuous phase. Water-in-oil gel emulsions of water/Ci4E4/oil 90/4/6 wt%, where C14E4 is a technical grade poly(oxyethylene) tetradecyl ether surfactant, with an average of four moles of ethylene oxide per surfactant molecule and oil can be octane, decane, dodecane, tetradecane, hexadecane, or squalane, were typically chosen as reaction media [23, 26]. 

Gel emulsions were applied successfully for the first time in aldol additions of DHAP to phenylacetaldehyde and benzyloxyacetaldehyde as model aldehydes catalyzed by RAMA [24]. The first interesting observation was that the stability of RAMA in water-in-oil gel emulsions improved by 25-fold compared to that in dimethylformamide/water l/4v/v co-solvent mixture. The reported experimental data concluded that both the highest enzymatic activities and equilibrium yields were observed in water-in-oil gel emulsion systems with the lowest water-oil interfacial tension attained with the most hydrophobic oil component (i.e. tetradecane, hexadecane, and squalane). 

Figure. 10.7. Velocity dispersion in n-tetradecane in water emulsions at different concentrations. (A) 5%. (B) 10%.

McClements and Dungan reported, based on light scattering measurements, that the Sauter or surface-volume mean diameter of drops in a dilute emulsion of n-hexadecane in water remained constant while the number of drops decreased with time during solubilization of the hydrocarbon into a 2 wt% solution of Tween 20 (sorbitan monolaurate). Weiss et al. found similar results for the same surfactant with n-tetradecane and n-octadecane. This result, which seems surprising in... 

Rather interesting demulsification methods were proposed recently [245] the use of membranes both of hydrophilic and hydrophobic nature to break down w/o emulsions and w/o/s mixtures. Hydrophobic membranes had pore sizes from 0.02 to 0.2 pm, and the dispersed aqueous phase droplet sizes ranged from 1 to 5 pm. The effect of water droplet retention is present even though the molecular weight of the water molecule (18) is much smaller than that of tetradecane (198) which was used as a model. 

The oxidation rate of emulsions of ethyl linoleate (EL) diluted with n-tetradecane in the presence of Tween 20 was studied in [301], The emulsions had an initial droplet diameter of 0.3 pm and total oil contents of 5 wt.% (EL-tetradecane). At 1% EL in oil, oxidation proceeds at a slow rate. At 20% EL in oil, the oxidation rate was rapid initially and then slowed down with time. In the absence of tetradecane, the oxidation rate was slow at first, and then increased with time. In all cases, the oxidation remained high in the presence of emulsifier. 

Tetradecane was emulsified at 25°C in two 0.5% (w/w) surfactant solutions (a) Ci2H25-(OCH2CH2)sOH (b) Ci2H2s0S03Na. What class of emulsion would you expect in each case What would you expect to be the natures of the two emulsions when heated to 50°C ... 

Nanoparticles in the GML/tetradecane/water system could also be formed in the presence of clay particles. The authors assumed a Pickering emulsion-like stabilization by the clay particles which are of disk-like shape with about Inm thickness and 30 nm diameter. Detailed information about the stabilization mechanism within these systems remains, however, still to be obtained. The use of clay particles as stabilizers holds some promise with regard to the preparation of "emulsifier-free" systems which are very interesting for pharmaceutical purposes. Hydrolysis of the monoglyceride was, however, pronounced in these dispersions due to the comparatively high pH introduced by the clay particle suspension. 

FIG. 2 Competitive adsorption of P-lactoglobulin + Tween 20 at the oil-water interface. R is the Tween 20/P-lactoglobulin molar ratio. F (triangles), concentration of P-lactoglobulin on the surface of oil droplets in the emulsion (0.45 wt% protein, 10 wt% n-tetradecane, pH 7) T (circles), apparent surface shear viscosity after 5 h adsorption from a 10 wt% aqueous protein solution (pH 7, 25°C). (From Ref. 23.)... 

FIG. 11 Crystallization thermogram for the mixed emulsion containing 15 wt% n-hexa-decane droplets and 15 wt% tetradecane droplets. 

As the number of moles of oil in a droplet is proportional to the enthalpy of crystallization [23], we calculated the area of the hexadecane peak A with respect to time to quantify the kinetics of diffusion of tetradecane into hexadecane drops. Considering that at fo = 0 the area A is the reference one, we report in Fig. 14 the ratio A/Ao versus time. This ratio is assumed to vary between 1 (f = to) and 0 (f = U, end of transfer). The ratio decreases almost exponentially, and 4 is reached after approximately 15 h of diffusion. The same kinds of results were reported by Clausse et al. [23] for water-in-oil emulsions, but in that case the equilibrium time was much smaller than in our case (about 1 h). 

Figure 3 Comparing ELM extraction of copper in a SC and in a HFC. Aqueous phase was 1000 ppm copper solution at pH 5.36. Emulsion contained 3 wt.% ECA5025 as surfactant, 5 wt.% LDC 84 as extractant and 18 wt.% 6N H2SO4 as stripping agent Solvent used was n-tetradecane. SC was operated at 400 rpm. In the HFC run, aqueous phase flowed through shell side at 40 ml/min and emulsion was stationary in the HFC tube. The ratio of aqueous phase to emulsion was 10 to 1.

At CMCs of 2-5 X 10 M, the mannosylerythritol lipids reduced the surface tension of water and the interfadal tension between water and n-tetradecane to about 28 and 2 mN/m, respectively [60]. To examine the emulsifying activity (o/w emulsions, optical density measurements at 620 nm) of MEL-A and B produced from n-octadecane, various oils were used [55]. They showed much higher activity for soybean oil than did Tween 80 at 50 mg/L. With respect to -tetradecane, the activity of MEL-A was higher than that of Tween 80 whereas that of MEL-B was similar. MEL-SY16 from C. antarctica sp SY16 lowered the water surface tension to 29 mN/m at CMC of 1.5 X 10 M (10 mg/L) the minimum interfacial tension was 0.1 mN/m against kerosene [57]. Evaluating the properties of mannosylerythritol lipids from Pseudozyma Candida ATCC 20509, it was observed that the culture broth decreased the water surface tension to 35 mN/m [56]. 

Figure 7.16 Release profiles (%) of flumethrin at 25°C from OAV/O multiple emulsions prepared with different external oil phases MCT, o K-decane, K-dodecane, a n-tetradecane, a Q7-9120 20 Cs, Q7-9120 100 Cs, cyclomethicone 5-NF, x. The external surfactant is 10wt% 3225C surfactant. The primary emulsion consists of 30wt% oU-in-water where the oil consists of flumethrin (50wt%) dissolved in MCT and stabilized with 5wt% WPI/xanthan gum (4/0.3.) The multiple emulsion contains 20wt% primary emulsion so that the overall flumethrin concentration in the final multiple emulsion is 3wt%. (Adapted from Benichou et al., 2007b.)...

Figure 56 Droplet size distribution of 5 wt% tetradecane-in-water emulsion prepared with 0.5 wt% guar gum, (A) inunediately after preparation, ( ) after 1 week, and ( ) after 1 month of aging at room temperature. (From Ref. 163.)... 

Figure 57 The birefringency effect of 5 wt% tetradecane-in-water emulsions stabilized by (left) 0.5 wt% guar gum and (right) 0.5 wt% fenugreek gum.

Figure 59 Emulsification stability index (ESI) vs. POG concentration in emulsions of 5 wt% tetradecane in water measured 7 days after preparation.

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